Electrophotographic photoreceptor, process cartridge, image forming apparatus, and imide compound

ABSTRACT

An electrophotographic photoreceptor includes a conductive substrate; a photosensitive layer provided on the conductive substrate; and an undercoating layer that is provided between the conductive substrate and the photosensitive layer and includes a charge transport material containing at least one of imide compounds represented by Formula (1) or (2): 
     
       
         
         
             
             
         
       
         
         
           
             (in Formulas (1) and (2), R 10 , R 11 , R 20 , or R 21  independently represents a group represented by Formula (3) or (4) where X represents a monovalent organic group having at least one of an alkyl group, an alkylene group, an ether group, an ester group, and a keto group, a halogen atom, a nitro group, an aralkyl group, or an aryl group, Y represents a sulfur atom or an oxygen atom, n represents an integer of 0 to 2, and when n represents 2, two X&#39;s may be the same or different), and an imide compound is represented by Formula (1A) where Ar represents an aromatic group having 6 to 18 carbon atoms except for a tetravalent perylene group, X 1  and X 2  each independently represent a nitrogen atom or a substituted or unsubstituted carbon atom, Y 1  and Y 2  each independently represent an oxygen atom, a sulfur atom, a selenium atom, or NH, and R 1  and R 2  each independently represent a hydrogen atom or a monovalent organic group:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2018-076119 filed on Apr. 11, 2018 andJapanese Patent Application No. 2018-076120 filed on Apr. 11, 2018.

BACKGROUND (i) Technical Field

The present invention relates to an electrophotographic photoreceptor, aprocess cartridge, an image forming apparatus, and an imide compound.

(ii) Related Art

In the related art, as an electrophotographic image forming apparatus,an apparatus that sequentially performs steps such as charging, formingan electrostatic latent image, developing, transferring, and cleaning,by using an electrophotographic photoreceptor is widely known.

As the electrophotographic photoreceptor, there is known afunction-separated photoreceptor in which a charge generation layer thatgenerates charge and a charge transport layer that transports the chargeare stacked on a substrate having conductivity such as aluminum or asinglelayer type photoreceptor in which the same layer plays a functionof generating charge and a function of transporting charge.

Japanese Patent No. 4411232 discloses a method of manufacturing anelectrophotographic photoreceptor, the method including: (a) forming anintermediate layer on a conductive support using an intermediate layercoating material containing particles of polynaphthyl diimide polymer;and (b) forming a photosensitive layer on the intermediate layer.

Japanese Patent No. 4498123 discloses an electrophotographicphotoreceptor including a hole transport layer containing a holetransport substance and a charge generation layer containing an electrontransport substance in an amount of 21% to 50% by weight with respect toa charge generation substance and an electrophotographic apparatus usingthe electrophotographic photoreceptor. In addition, there is alsodisclosed that ghost improves by adding the electron transport substancesuch as a fluorine-containing bisimide compound.

Japanese Patent No. 5975942 discloses an electrophotographicphotoreceptor including a support, an electron transport layer, and aphotosensitive layer in this order, in which the electron transportlayer is a cured product of a composition including an electrontransport substance having a polymerizable functional group, athermoplastic resin having a polymerizable functional group, and acrosslinking agent and includes a carbon atom, a nitrogen atom, and anoxygen atom which have a standard deviation in a predetermined rangewhen analyzed by X-ray photoelectron spectroscopy.

Japanese Patent No. 5147274 discloses a naphthalene tetracarboxylic aciddiimide compound having a structure in which a phenyl group or ahydroxyalkyl group having a substituent is bonded to nitrogen atoms oftwo imide groups. In addition, there is also disclosed that thenaphthalene tetracarboxylic acid diimide compound may be contained in anintermediate layer.

Japanese Patent No. 5064815 discloses a naphthalene tetracarboxylic aciddiimide compound having a structure in which a phenyl group having asubstituent is bonded to nitrogen atoms of two imide groups.

In addition, JP-A-2005-208618 discloses an electrophotographicphotoreceptor including: a charge generation layer including a chargegeneration substance and a hole transport layer which is provided on thecharge generation layer and contains a hole transport substance, inwhich the charge generation layer contains an electron transportsubstance. In addition, there is also disclosed that the naphthalenetetracarboxylic acid diimide compound having a thiophene group may beused as the electron transport substance.

JP-A-07-253682 discloses an electrophotographic photoreceptor includinga photosensitive layer on a conductive support, in which a perylenetetracarboxylic acid diimide having a thiazole group or a benzothiazolegroup is contained in the photosensitive layer.

In addition, in the related art, various charge transport materials usedfor electrophotographic photoreceptors and the like are known.

For example, JP-A-4-285670 discloses an electrophotographicphotoreceptor including a novel diphenoquinone compound and aphotosensitive layer containing the compound as a charge transportmaterial.

JP-A-5-25136 discloses a novel naphthalene dicarboxylic acid imidecompound.

JP-A-4-338969 discloses an electrophotographic photoreceptor including aconductive substrate and a photosensitive layer that is provided on theconductive substrate and contains a perylene pigment having a specificX-ray diffraction peak as a charge generation material.

JP-A-5-25174 discloses a novel naphthalene tetracarboxylic acid diimidecompound.

JP-A-2002-116565 discloses an electrophotographic photoreceptor in whicha conductive substrate, an organic photosensitive layer that is providedon the conductive substrate and contains a novel naphthylene diimidederivative, and an inorganic surface protective layer provided on theorganic photosensitive layer are laminated.

JP-A-11-343290 and JP-A-11-343291 disclose a novel naphthalenetetracarboxylic acid diimide derivative and an electrophotographicphotoreceptor containing the novel naphthalene tetracarboxylic aciddiimide derivative.

JP-A-2004-262813 discloses a novel naphthalene tetracarboxylic aciddiimide derivative and an electrophotographic photoreceptor including aphotosensitive layer containing the novel naphthalene tetracarboxylicacid diimide derivative.

JP-A-07-253682 discloses an electrophotographic photoreceptor includinga conductive support and a photosensitive layer that is provided on theconductive support and contains a perylene pigment.

JP-A-2005-154444 discloses a naphthalene tetracarboxylic acid diimidederivative compound and an electrophotographic photoreceptor including aphotosensitive layer containing the naphthalene tetracarboxylic aciddiimide derivative compound as an electron transport substance.

SUMMARY

Aspects of non-limiting embodiments of the present disclosure relate toan electrophotographic photoreceptor that prevents an increase of theresidual potential when images are formed repeatedly, as compared with acase of an electrophotographic photoreceptor including a conductivesubstrate, a photosensitive layer provided on the conductive substrate,and an undercoating layer that is provided between the conductivesubstrate and the photosensitive layer and contains Compound (A),Compound (B), or Compound (C) described in the working examplesdescribed later as an imide compound and a novel imide compound havingan electron transporting ability.

Aspects of certain non-limiting embodiments of the present disclosureovercome the above disadvantages and other disadvantages not describedabove. However, aspects of the non-limiting embodiments are not requiredto overcome the disadvantages described above, and aspects of thenon-limiting embodiments of the present disclosure may not overcome anyof the problems described above.

According to a first aspect of the present disclosure, there is providedan electrophotographic photoreceptor including:

a conductive substrate;

a photosensitive layer provided on the conductive substrate; and

an undercoating layer that is provided between the conductive substrateand the photosensitive layer and includes a charge transport materialcontaining at least one of imide compounds represented by Formula (1) or(2):

(in Formulas (1) and (2), R¹⁰, R¹¹, R²⁰, or R²¹ independently representsa group represented by Formula (3) or (4); and

in Formulas (3) and (4), X represents a monovalent organic group havingat least one of an alkyl group, an alkylene group, an ether group, anester group, and a keto group, a halogen atom, a nitro group, an aralkylgroup, or an aryl group, Y represents a sulfur atom or an oxygen atom, nrepresents an integer of 0 to 2, and when n represents 2, two X's may bethe same or different).

According to a second aspect of the present disclosure, there isprovided an imide compound represented by Formula (1A):

(in Formula (1A), Ar represents an aromatic group having 6 to 18 carbonatoms except for a tetravalent perylene group, X¹ and X² eachindependently represent a nitrogen atom or a substituted orunsubstituted carbon atom, and Y¹ and Y² each independently represent anoxygen atom, a sulfur atom, a selenium atom, or NH, and R¹ and R² eachindependently represent a hydrogen atom or a monovalent organic group).

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a schematic perspective diagram illustrating an example of alayer configuration of an electrophotographic photoreceptor according tothe exemplary embodiment;

FIG. 2 is a schematic sectional diagram of an example of an imageforming apparatus according to the exemplary embodiment;

FIG. 3 is a schematic perspective diagram of another example of theimage forming apparatus according to the exemplary embodiment;

FIG. 4 is a schematic partial sectional diagram illustrating anotherexample of the layer configuration of the electrophotographicphotoreceptor according to the exemplary embodiment;

FIG. 5 is a graph showing a ¹H-NMR spectrum of Exemplary Compound(1A-23);

FIG. 6 is a graph showing a ¹H-NMR spectrum of Exemplary Compound(1A-30);

FIG. 7 is a graph showing a ¹H-NMR spectrum of Exemplary Compound(1A-31); and

FIG. 8 is a graph showing a ¹H-NMR spectrum of Exemplary Compound(1A-33).

DETAILED DESCRIPTION

First, the first aspect of the present disclosure will be described.These descriptions and examples are illustrative of exemplaryembodiments and do not limit the scope of the invention.

—Electrophotographic Photoreceptor—

An electrophotographic photoreceptor according to the exemplaryembodiment includes a conductive substrate; a photosensitive layerprovided on the conductive substrate; and an undercoating layer that isprovided between the conductive substrate and the photosensitive layerand includes a charge transport material containing at least one ofimide compounds represented by Formula (1) or (2). In this case, inFormulas (1) and (2), moieties of R¹⁰, R¹¹, R²⁰, and R²¹ eachindependently represent a group represented by a thiazole group, abenzothiazole group, an oxazole group, or a benzoxazole group, which mayhave a substituent.

In the electrophotographic photoreceptor of the related art, sinceelectron transportability of the undercoating layer is low, a residualpotential tends to easily increase when images are formed repeatedly dueto matters such as energy matching with a charge generation layer. Whenthe residual potential is likely to increase in the undercoating layer,density unevenness or the like of an image becomes likely to occur.

On the other hand, in the electrophotographic photoreceptor according tothe exemplary embodiment, an increase of the residual potential whichmay be caused when images are formed repeatedly is prevented by havingthe configuration. Detailed reasons for achieving the above effects arenot always clear, but may be considered as follows.

For example, when a phthalocyanine pigment is used as a chargegeneration material, the imide compound represented by Formula (1) or(2) having a thiazole group, a benzothiazole group, an oxazole group, ora benzoxazole group is expected to be easily receive electrons and havesufficient electron transportability, and it is thus considered that anincrease of the residual potential which may be caused when images areoutput repeatedly is prevented.

Hereinafter, a layer configuration of the electrophotographicphotoreceptor according to the exemplary embodiment will be described.

An electrophotographic photoreceptor 7A shown in FIG. 1 is a so-calledfunction-separated photoreceptor (or a laminated photoreceptor), and hasa structure in which an undercoating layer 1 is provided on a conductivesubstrate 4, and a charge generation layer 2 and a charge transportlayer 3 are sequentially formed thereon. In the electrophotographicphotoreceptor 7A, the photosensitive layer 5 is formed by the chargegeneration layer 2 and the charge transport layer 3. Theelectrophotographic photoreceptor according to the exemplary embodimentmay be configured to include other layers, for example, a protectivelayer.

Hereinafter, each layer of the electrophotographic photoreceptoraccording to the exemplary embodiment will be described in detail.Descriptions will be given without reference numerals.

[Undercoating Layer]

Hereinafter, the undercoating layer will be described.

The undercoating layer according to the exemplary embodiment includes acharge transport material containing at least one of imide compoundsrepresented by Formula (1) or (2). The undercoating layer according tothe exemplary embodiment may contain metal oxide particles, a curingresin, and other additives.

(Charge Transport Material)

Hereinafter, the charge transport material will be described.

The charge transport material according to the exemplary embodimentcontains at least one of imide compounds represented by Formula (1) or(2). The charge transport material may contain other charge transportmaterials.

In Formulas (1) and (2), R¹⁰, R¹¹, R²⁰, or R²¹ independently representsa group represented by Formula (3) or (4).

In Formulas (3) and (4), X represents a monovalent organic group havingat least one of an alkyl group, an alkylene group, an ether group, anester group, and a keto group, a halogen atom, a nitro group, an aralkylgroup, or an aryl group.

In Formulas (3) and (4), Y represents a sulfur atom or an oxygen atom. nrepresents an integer of 0 to 2. Here, when n represents 2, two X's maybe the same or different.

The monovalent organic group is a monovalent organic group formed bycombining at least one of an alkyl group, an alkylene group, an ethergroup, an ester group, and a keto group, is preferably an alkyl group oran alkylene group each having 1 to 12 carbon atoms, and is morepreferably an alkyl group or an alkylene group each having 1 to 8 carbonatoms.

Examples of the monovalent organic group include the following groups.In the following linking groups, “*” represents a moiety linked to R¹⁰,R¹¹, R²⁰, or R²¹ in Formula (1) or (2). R^(A) represents an alkyl group,and R^(B) represents an alkylene group. n₁ represents an integer of 1 ormore. When n₁ represents an integer of 2 or more, plural R^(B)'s may bethe same or different.

-   -   —R^(A)    -   —R^(B)—C(═O)—R^(A)    -   —R^(B)—O—R^(A)    -   —O—R^(A)    -   —C(═O)—R^(A)    -   —C(═O)—O—R^(A)    -   —R^(B)—C(═O)—O—R^(A)    -   —R^(B)—C(═O)—O—(R^(B)—O)n₁-R^(A).

In Formulas (3) and (4), the alkyl group represented by X corresponds toR^(A).

In Formulas (3) and (4), the alkylene group represented by X correspondsto R^(B).

Examples of the alkyl group represented by R^(A) include a substitutedor unsubstituted alkyl group.

Examples of the unsubstituted alkyl group represented by R^(A) include alinear alkyl group having 1 to 12 carbon atoms (preferably 1 to 8 carbonatoms) and a branched alkyl group having 3 to 10 carbon atoms(preferably having 5 to 8 carbon atoms.

Examples of the linear alkyl group having 1 to 12 carbon atoms include amethyl group, an ethyl group, a n-propyl group, a n-butyl group, an-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, an-nonyl group, a n-decyl group, a n-undecyl group, and a n-dodecylgroup.

Examples of the branched alkyl group having 3 to 10 carbon atoms includean isopropyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, an isopentyl group, a neopentyl group, a tert-pentyl group, anisohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptylgroup, a sec-heptyl group, a tert-heptyl group, an isooctyl group, asec-octyl group, a tert-octyl group, an isononyl group, a sec-nonylgroup, a tert-nonyl group, an isodecyl group, a sec-decyl group, and atert-decyl group.

Among the above groups, as the unsubstituted alkyl group, lower alkylgroups such as the methyl group and the ethyl group are preferable.

As the alkylene group represented by R^(B), groups having a structure inwhich one hydrogen is further removed from the alkyl group representedby R^(A) are preferable.

Examples of the substituent in the alkyl group represented by R^(A)include an alkoxy group having 1 to 4 carbon atoms, an unsubstitutedaryl group, a phenyl group substituted with an alkyl group or alkoxygroup, having 1 to 4 carbon atoms, an aralkyl group having 7 to 10carbon atoms, a hydroxyl group, a carboxyl group, a nitro group, and ahalogen atom (chlorine, iodine, bromine).

Examples of the alkoxy group of the alkoxy-substituted alkyl groupinclude a linear or branched alkoxy group having 1 to 10 (preferably 1to 6 and more preferably 1 to 4) carbon atoms. In addition, examples ofthe aryl group of the aryl-substituted alkyl group include the samegroups as the unsubstituted aryl group represented by X in Formulas (3)and (4) to be described later.

Examples of the halogen atom represented by X in Formulas (3) and (4)include a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom.

Examples of a substituted or unsubstituted aralkyl group represented byX in Formulas (3) and (4) include an aralkyl group having 7 to 15(preferably 7 to 14) carbon atoms.

Specific examples of the substituted or unsubstituted aralkyl groupinclude a benzyl group, a phenylethyl group, a vinylbenzyl group, and ahydroxyphenylmethyl group.

Examples of the aryl group represented by X in Formulas (3) and (4)include a substituted or unsubstituted aryl group.

The unsubstituted aryl group represented by X in Formulas (3) and (4) ispreferably an aryl group having 6 to 30 carbon atoms, and examplesthereof include a phenyl group, a biphenyl group, a 1-naphthyl group, a2-naphthyl group, a 9-anthryl group, a 9-phenanthryl group, a 1-pyrenylgroup, a 5-naphthacenyl group, a 1-indenyl group, a 2-azulenyl group, a9-fluorenyl group, a terphenyl group, a quarterphenyl group, o-, m-, andp-tolyl groups, a xylyl group, o-, m-, and p-cumenyl groups, a mesitylgroup, a pentalenyl group, a binaphthalenyl group, a tanaphthalenylgroup, a quaternaphthalenyl group, a heptarenyl group, a biphenylenylgroup, an indacenyl group, a fluoranthenyl group, an acenaphthylenylgroup, an aceanthrylenyl group, a phenalenyl group, a fluorenyl group,an anthryl group, a bianthracenyl group, a teranthracenyl group, aquater anthracenyl group, an anthraquinolyl group, a phenanthryl group,a triphenylenyl group, a pyrenyl group, a chrysenyl group, anaphthacenyl group, a preadenyl group, a picenyl group, a perylenylgroup, a pentaphenyl group, a pentacenyl group, a tetraphenylenyl group,a hexaphenyl group, a hexacenyl group, a rubicenyl group, a coronenylgroup, a trinaphthylenyl group, a heptaphenyl group, a heptacenyl group,a pyranthrenyl group, and an ovalenyl group. Among the above groups, thephenyl group is preferable.

Examples of the substituent in the aryl group represented by X inFormulas (3) and (4) include an alkyl group, an alkoxy group, and ahalogen atom (chlorine, iodine, bromine). Examples of the alkyl group ofthe alkyl-substituted aryl group include a linear or branched alkylgroup having 1 to 10 (preferably 1 to 6 and more preferably 1 to 4)carbon atoms. Examples of the alkoxy group of the alkoxy-substitutedaryl group include a linear or branched alkoxy group having 1 to 10(preferably 1 to 6 and more preferably 1 to 4) carbon atoms.

From the viewpoint of preventing an increase of the residual potentialwhich may be caused when images are output repeatedly, X represented inFormula (3) or (4) is preferably a monovalent organic group having atleast one of an alkyl group, an alkylene group, an ether group, an estergroup, and a keto group.

Exemplary compounds of the imide compounds represented by Formula (1) or(2) are shown below, but the imide compounds are not limited thereto.

Other charge transport materials are not particularly limited, butexamples thereof include electron transport compounds such as a quinonecompound, e.g., p-benzoquinone, chloranil, bromanil, and anthraquinone;a tetracyanoquinodimethane compound; a fluorenone compound, e.g.,2,4,7-trinitrofluorenone; a xanthone compound; a benzophenone compound;a cyanovinyl compound; an ethylene compound; and a9-dicyanomethylenefluorene compound.

In addition, hole transporting compounds such as a triarylaminecompound, a benzidine compound, an arylalkane compound, anaryl-substituted ethylene compound, a stilbene compound, an anthracenecompound, and a hydrazone compound are also exemplified.

These charge transport materials may be used alone or in combination oftwo or more thereof, though the other charge transport materials are notlimited thereto.

A content of the other charge transport materials contained in theundercoating layer is not particularly limited, but is preferably from0% by weight to 20% by weight with respect to the imide compoundsrepresented by Formula (1) or (2), and more preferably from 0% by weightto 10% by weight.

A content of the imide compounds represented by Formula (1) or (2) inthe undercoating layer is preferably from 10% by weight to 80% byweight, from the viewpoint of preventing an increase of the residualpotential which may be caused when images are output repeatedly, andmore preferably from 20% by weight to 70% by weight from the viewpointof uniformity of a film at the time of coating.

(Inorganic Particles)

Hereinafter, inorganic particles will be described.

The undercoating layer according to the exemplary embodiment may furtherinclude inorganic particles besides the charge transport materialcontaining the imide compound represented by Formula (1) or (2).

Examples of the inorganic particles include inorganic particles having apowder resistance (volume resistivity) from 1.0×10² (Ω·cm) to 1.0×10¹¹(Ω·cm).

Examples of the inorganic particles having the resistance value includemetal oxide particles of zinc oxide, titanium oxide, tin oxide, aluminumoxide, indium oxide, silicon oxide, magnesium oxide, barium oxide,molybdenum oxide, and the like. These may be used alone and two or morekinds thereof may be used in combination.

Among the above particles, from the viewpoint of preventing from theviewpoint of preventing an increase of the residual potential which maybe caused when images are output repeatedly, at least one or moreselected from the group consisting of zinc oxide, titanium oxide, andtin oxide is preferable as the metal oxide particles.

A specific surface area of the inorganic particles by a BET method ispreferably, for example, 10 m²/g or more. The BET specific surface areais measured using a nitrogen substitution method. Specifically, the BETspecific surface area is measured by a three point method using anSA3100 specific surface area measuring apparatus (manufactured byBeckman Coulter, Inc.).

A volume average particle diameter of the inorganic particles ispreferably, for example, from 50 nm to 2,000 nm (more preferably from 60nm to 1,000 nm).

The volume average particle diameter is measured using a laserdiffraction type particle size distribution measuring apparatus (LA-700:manufactured by Horiba. Ltd.). As a measuring method, 2 g of ameasurement sample is added to 50 ml of a 5% aqueous solution of asurfactant, preferably sodium alkylbenzenesulfonate, and dispersed for 2minutes with an ultrasonic disperser (1,000 Hz) to prepare a sample, andthe sample is measured. The volume average particle diameter providedper each channel obtained is accumulated from the smaller one of thevolume average particle diameter, and when the accumulated volumeaverage particle diameter reached 50% based on the sum total, the volumeaverage particle diameter accumulated finally is taken as the volumeaverage particle diameter.

From the viewpoint of preventing from the viewpoint of preventing anincrease of the residual potential which may be caused when images areoutput repeatedly, a content of the inorganic particles, specificallythe metal oxide particles is preferably from 10% by weight to 80% byweight, and more preferably from 20% by weight to 70% by weight withrespect to the undercoating layer.

The inorganic particles may be subjected to a surface treatment. Two ormore kinds of the inorganic particles, which are subjected to differentsurface treatments or have different particle diameters, may be mixed tobe used.

Examples of the surface treatment agent include a silane coupling agent,a titanate coupling agent, an aluminum coupling agent, and a surfactant.In particular, the silane coupling agent is preferable, and a silanecoupling agent having an amino group is more preferable.

Examples of the silane coupling agent having an amino group include3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, andN,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, but are notlimited thereto.

Two or more kinds of the silane coupling agents may be mixed to be used.For example, the silane coupling agent having an amino group and theother silane coupling agent may be used in combination. Examples of theother silane coupling agent include vinyltrimethoxysilane,3-methacryloxypropyl-tris(2-methoxyethoxy)silane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane,3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and3-chloropropyltrimethoxysilane, but are not limited thereto.

The surface treatment method with the surface treatment agent may be anymethod as long as it is a known method, and either a dry method or a wetmethod may be used.

From the viewpoint of improving dispersibility, for example, athroughput of the surface treatment agent is preferably from 0.5% byweight to 10% by weight with respect to the inorganic particles.

Here, the undercoating layer may contain an electron accepting compound(acceptor compound) together with the inorganic particles, from theviewpoint of improving long-term stability of electric characteristicsand carrier blocking property.

Examples of the electron accepting compound include electron transportsubstances such as: quinone compounds such as chloranil and bromoanil; atetracyanoquinodimethane compound; fluorenone compounds such as2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazolecompounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole,2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; a xanthone compound; athiophene compound; and diphenoquinone compounds such as3,3′,5,5′-tetra-t-butyldiphenoquinone.

In particular, as the electron accepting compound, a compound having ananthraquinone structure is preferable. As the compound having ananthraquinone structure include a hydroxyanthraquinone compound, anaminoanthraquinone compound, and an aminohydroxyanthraquinone compoundare preferable, and specifically, for example, anthraquinone, alizarin,quinizarin, antharufine, purpurin, and the like are preferable.

The electron accepting compound may be contained by being dispersed inthe undercoating layer together with the inorganic particles or may becontained in a state of being attached to the surfaces of the inorganicparticles.

Examples of a method of attaching the electron accepting compound to thesurfaces of the inorganic particles include a dry method or a wetmethod.

The dry method is, for example, a method in which while stirringinorganic particles with a mixer or the like having a large shear force,an electron accepting compound is dropped directly or by being dissolvedin an organic solvent, and sprayed together with dry air or nitrogen gasto attach the electron accepting compound to the surfaces of theinorganic particles. When dropping or spraying the electron acceptingcompound, the dropping or spraying the electron accepting compound maybe carried out at a temperature equal to or lower than a boiling pointof the solvent. After dropping or spraying the electron acceptingcompound, baking may further be carried out at 100° C. or higher. Bakingis not particularly limited as long as the baking is carried out at atemperature and time at which electrophotographic characteristics areobtained.

The wet method is, for example, a method in which an electron acceptingcompound is added while dispersing inorganic particles in a solvent bystirring, ultrasonic wave, sand mill, attritor, ball mill, or the like,and is stirred or dispersed, and then the solvent is removed to attachthe electron accepting compound to the surfaces of the inorganicparticles. In the solvent removal method, the solvent is removed, forexample, by filtration or distillation. After removing the solvent,baking may further be carried out at 100° C. or higher. Baking is notparticularly limited as long as the baking is carried out at atemperature and time at which electrophotographic characteristics areobtained. In the wet method, moisture contained in the inorganicparticles may be removed before adding the electron accepting compound.Examples of this method include a method of removing the moisture whilestirring and heating in a solvent, and a method of removing the moistureby azeotropic distillation with a solvent.

The attachment of the electron accepting compound may be carried outbefore or after the inorganic particles are subjected to the surfacetreatment with the surface treatment agent. Also, the attachment of theelectron accepting compound and the surface treatment with the surfacetreatment agent may be carried out at the same time.

A content of the electron accepting compound may be, for example, from0.01% by weight to 20% by weight, and is preferably from 0.01% by weightto 10% by weight in the inorganic particles.

(Curing Resin)

Hereinafter, the curing resin will be described.

The undercoating layer according to the exemplary embodiment may beconfigured to further contain the curing resin.

The undercoating layer is preferably a layer configured by a cured film(including a crosslinked film) in which the curing resin is cured.

The curing resin contained in the undercoating layer is not particularlylimited as long as the curing resin does not deteriorate the electrontransportability and electrification characteristic of the imidecompound, and known curing resin may be used. Examples of the curingresin include thermosetting high-molecular compounds such as polyimide,a urethane resin, an epoxy resin, a phenol resin, a urea resin, amelamine resin, an unsaturated polyester resin, a diallyl phthalateresin, an alkyd resin, a polyamino bismaleimide, a furan resin, a urearesin, a phenol-formaldehyde resin, and an alkyd resin. Examples of thecuring resin also include polymer compounds such as an acetal resin suchas polyvinyl butyral, a polyvinyl alcohol resin, casein, a polyamideresin, a cellulose resin, gelatin, a polyester resin, a methacrylicresin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl acetateresin, a vinyl chloride-vinyl acetate-maleic anhydride resin, a siliconeresin, a silicone-alkyd resin, and a phenol-formaldehyde resin. Further,charge transport resin having a charge transport group and a conductiveresin (such as polyaniline) may be used as the curing resin.

Among the resins, as the curing resin, at least one selected from thegroup consisting of a phenol resin, a melamine resin, a guanamine resin,and a urethane resin is preferable and a urethane resin is morepreferable. In a case where two or more of these curing resins are usedin combination, a mixing ratio thereof is set as needed.

For example, in a case where the phenol resin and the melamine resin aremixed to be used, it is preferable to perform curing using an acidcatalyst. In a case where the urethane resin is used, it is preferableto perform curing using an amine catalyst or a metal catalyst. A contentthe catalyst used for curing is preferably from 0.01% by weight to 20%by weight and more preferably 0.1% by weight to 10% by weight, based on100% by weight of a solid content of the undercoating layer. A curingtemperature is preferably from room temperature to 200° C. and morepreferably from 100° C. to 150° C.

As the phenol resin, substituted phenols containing one hydroxyl groupsuch as resorcin, bisphenol, phenol, cresol, xylenol, paraalkylphenol,and paraphenylphenol; substituted phenols containing two hydroxyl groupssuch as catechol, resorcinol, and hydroquinone; bisphenols such asbisphenol A and bisphenol Z; monomethylolphenols obtained by reacting acompound having a phenol structure with formaldehyde, paraformaldehyde,or the like under an acid or alkali catalyst; dimethylol phenols;monomers of trimethylolphenols and mixtures thereof; multimers oftrimethylolphenols; mixtures of monomers and polymers oftrimethylolphenols; and the like are used. A molecule in which repeatingstructural units of a molecule is from 2 to 20 is referred to as amultimer, and a molecule in which the repeating structural units of amolecule is less than the above range is referred to as a monomer.

Examples of the melamine resin and the guanamine resin include amelamine resin and a guanamine resin, having an unmodified methylolgroup, an alkyl ether modified methylol group, an imino modifiedmethylol group, a methylol group having an unmodified moiety and animino modified moiety, and the like. Among the above resins, from theviewpoint of the stability of the coating liquid, the melamine resin andthe guanamine resin, having the alkyl ether modified methylol group arepreferable.

Examples of a raw material for obtaining the urethane resin includepolyfunctional isocyanate and isocyanurate. In addition, blockedisocyanate having a structure in which the above-describedpolyfunctional isocyanate and isocyanurate are masked with a blockingagent (such as alcohol and ketone) may also be used. Among the above rawmaterials, from the viewpoint of the stability of the coating liquid,the raw material for obtaining the urethane resin is preferably theblocked isocyanate or isocyanurate.

Examples of the acid catalyst used for curing include: aliphaticcarboxylic acids such as acetic acid, chloroacetic acid, trichloroaceticacid, trifluoroacetic acid, oxalic acid, maleic acid, malonic acid, andlactic acid; aromatic carboxylic acids such as benzoic acid, phthalicacid, terephthalic acid, and trimellitic acid; and protonic acids suchas sulfonic acids such as methanesulfonic acid, dodecylsulfonic acid,benzenesulfonic acid, dodecylbenzenesulfonic acid, andnaphthalenesulfonic acid. In addition, a thermally latent protonic acidcatalyst in which the protonic acids are blocked with a base may beused. Among the above catalysts, from the viewpoint of storagestability, the thermally latent protonic acid catalyst is preferable asthe acid catalyst used for curing.

Examples of a specific commercial product of the acid catalyst include“NACURE 2501” (toluenesulfonic acid dissociation, methanol/isopropanolsolvent, from pH 6.0 to pH 7.2, and dissociation temperature of 80° C.),“NACURE 2107” (p-toluenesulfonic acid dissociation, isopropanol solvent,from pH 8.0 to pH 9.0, and dissociation temperature of 90° C.), “NACURE2500” (p-toluenesulfonic acid dissociation, isopropanol solvent, from pH6.0 to pH 7.0, and dissociation temperature of 65° C.), “NACURE 2530”(p-toluenesulfonic acid dissociation, methanol/isopropanol solvent, frompH 5.7 to pH 6.5, and dissociation temperature of 65° C.), “NACURE 2547”(p-toluenesulfonic acid dissociation, aqueous solution, from pH 8.0 topH 9.0, and dissociation temperature of 107° C.), “NACURE 2558”(p-toluenesulfonic acid dissociation, ethylene/glycol solvent, from pH3.5 to pH 4.5, and dissociation temperature of 80° C.), “NACURE XP-357”(p-toluenesulfonic acid dissociation, methanol solvent, from pH 2.0 topH 4.0, and dissociation temperature of 65° C.), “NACURE XP-386”(p-toluenesulfonic acid dissociation, aqueous solution, from pH 6.1 topH 6.4, and dissociation temperature of 80° C.), “NACURE XC-2211”(p-toluenesulfonic acid dissociation, from pH 7.2 to pH 8.5, anddissociation temperature of 80° C.), “NACURE 5225” (dodecylbenzenesulfonic acid dissociation, isopropanol solvent, from pH 6.0 to pH 7.0,and dissociation temperature of 120° C.), “NACURE 5414” (dodecylbenzenesulfonic acid dissociation, xylene solvent, and dissociation temperatureof 120° C.), “NACURE 5528” (dodecylbenzene sulfonic acid dissociation,isopropanol solvent, from pH 7.0 to pH 8.0, and dissociation temperatureof 120° C.), “NACURE 5925” (dissociation of dodecylbenzenesulfonic acid,from pH 7.0 to pH 7.5, and dissociation temperature of 130° C.), “NACURE1323” (dinonylnaphthalenesulfonic acid dissociation, xylene solvent,from pH 6.8 to pH 7.5, and dissociation temperature of 150° C.), “NACURE1419” (dinonylnaphthalene sulfonic acid dissociation, xylene/methylisobutyl ketone solvent, and dissociation temperature of 150° C.),“NACURE 1557” (dinonylnaphthalenesulfonic acid dissociation,butanol/2-butoxyethanol solvent, from pH 6.5 to pH 7.5, and dissociationtemperature of 150° C.), “NACURE X49-110” (dinonylnaphthalene disulfonicacid dissociation, isobutanol/isopropanol solvent, from pH 6.5 to pH7.5, and dissociation temperature of 90° C.), “NACURE 3525”(dinonylnaphthalene disulfonic acid dissociation, isobutanol/isopropanolsolvent, from pH 7.0 to pH 8.5, and dissociation temperature of 120°C.), “NACURE XP-383” (dinonylnaphthalene disulfonic acid dissociation,xylene solvent, and dissociation temperature of 120° C.), “NACURE 3327”(dinonylnaphthalene disulfonic acid dissociation, isobutanol/isopropanolsolvent, from pH 6.5 to pH 7.5, and dissociation temperature of 150°C.), “NACURE 4167” (phosphate dissociation, isopropanol/isobutanolsolvent, from pH 6.8 to pH 7.3, and dissociation temperature of 80° C.),“NACURE XP-297” (phosphate dissociation, water/isopropanol solvent, frompH 6.5 to pH 7.5, and dissociation temperature of 90° C.), and “NACURE4575” (dissociation of phosphate, from pH 7.0 to pH 8.0, anddissociation temperature of 110° C.), which are manufactured by KingIndustries, Inc.

In the case of using a cured film obtained by curing the urethane resin,examples of the catalyst include an amine catalyst and a metal catalyst.The amine catalyst is not particularly limited, but examples thereofinclude 1,4-diazabicyclo(2,2,2)octane, N,N-dimethylcyclohexylamine,N-methyldicyclohexylamine, N,N,N′,N′-tetramethylpropylenediamine,N-ethylmorpholine, N-methylmorpholine, N,N-dimethylethanolamine,1,8-diaza-bicyclo[5,4,0]undecene-7(DBU), and salts thereof. The metalcatalyst is not particularly limited, but examples thereof includedibutyltin laurate and stannous octoate.

The presence or absence of the solvent when preparing the coating liquidis not particularly limited. The solvent may be used or not. In a caseof using the solvent for preparing the coating liquid, as the solvent,solvents such as: alcohols such as methanol, ethanol, propanol, butanol,cyclopentanol, and cyclohexanol; ketones such as acetone, methyl ethylketone, cyclopentanone, and cyclohexanone; ethers such astetrahydrofuran, diethyl ether, dioxane, cyclopentyl methyl ether, and2-methyl tetrahydrofuran; halogen such as methylene chloride andchloroform; aromatic compounds such as toluene, xylene, andethylbenzene; and esters such as ethyl acetate and butyl acetate may beused. Among the above solvents, as the solvent, a solvent having aboiling point of 150° C. or lower is preferable, in particular, asolvent having at least one kind of hydroxyl group (such as alcohols) oran ether solvent (such as tetrahydrofuran) is more preferable. One kindof the solvents may be used alone and two or more kinds thereof may beused by being mixed.

As the curing resin, a curing agent such as a polyfunctional epoxycompound or a polyfunctional isocyanate compound may also be used.

As the polyfunctional epoxy compound, a multifunctional epoxy derivativesuch as a diglycidyl ether compound, a triglycidyl ether compound, or atetraglycidyl ether compound, a haloepoxy compound, or the like may beused. Specific examples of the polyfunctional epoxy compound includeglycidyl ether compounds of polyhydric alcohols such as ethylene glycoldiglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycoldiglycidyl ether, polypropylene glycol diglycidyl ether, glyceryldiglycidyl ether, and glyceryl triglycidyl ether; glycidyl ethercompounds of aromatic polyhydric phenols such as bisphenol A diglycidylether; and halo-epoxy compounds such as epichlorohydrin, epibromohydrin,and (3-methyl epichlorohydrin.

As the polyfunctional isocyanate compound, compounds having three ormore isocyanate groups are preferable, and specific examples thereofinclude polyisocyanate monomers such as 1,3,6-hexamethylenetriisocyanate, lysine ester triisocyanate, 1,6,11-undecanetriisocyanate, 1,8-isocyanate-4-isocyanatomethyloctane, triphenylmethanetriisocyanate, and tris(isocyanatephenyl) thiophosphate. Among thecompounds having three or more isocyanate groups, from the viewpoints offilm-forming cracking resistance and ease of handling of the crosslinkedfilm finally obtained, modified products of derivatives, a prepolymer,or the like, obtained from the polyisocyanate monomers are morepreferably used.

As examples of these, a urethane-modified product obtained by modifyinga polyol with an excess of the trifunctional isocyanate compound, aburette-modified product obtained by modifying a compound having a ureabond with an isocyanate compound, and an allophanate-modified productobtained by adding an isocyanate to a urethane group are particularlypreferable. In addition to these, an isocyanurate modified product, acarbodiimide modified product, and the like are used.

A total content of the curing resin according to the exemplaryembodiment is preferably from 20% by weight to 50% by weight and morepreferably 30% by weight to 45% by weight, in the undercoating layer.

The undercoating layer may also contain various additives.

As additives, for example, resin particles may be added. Examples of theresin particles include known materials such as silicone resin particlesand crosslinked polymethylmethacrylate (PMMA) resin particles.

Hereinafter, the other properties of the undercoating layer will bedescribed.

A film thickness of the undercoating layer is preferably from 3 μm to 50μm and more preferably from 5 μm to 40 μm.

When the film thickness of the undercoating layer is 3 μm or more, thereis tendency of preventing leakage current from occurring. On the otherhand, when the film thickness of the undercoating layer is 50 μm orless, there is tendency of preventing an increase of the residualpotential which may be caused when images are formed repeatedly.

The film thickness of the undercoating layer is measured using an eddycurrent film thickness meter CTR-1500E manufactured by Sanko Denshi Co.,Ltd.

From the viewpoint of preventing lowering of electrificationcharacteristic and an increase of the residual potential which may becaused when images are formed repeatedly, the volume resistivity of theundercoating layer is preferably from 1.0×10⁴ (Ω·m) to 10×10¹⁰ (Ω·m),more preferably from 1.0×10⁶ (Ω·m) to 10×10⁸ (Ω·m), and still morepreferably from 1.0×10⁶ (Ω·m) to 10×10⁷ (Ω·m).

A method of preparing an undercoating layer sample to be used formeasuring the volume resistivity, from an electrophotographicphotoreceptor is as follows. For example, coating films such as a chargegeneration layer and a charge transport layer which cover theundercoating layer are removed using a solvent such as acetone,tetrahydrofuran, methanol, or ethanol, and a gold electrode is attachedon the exposed undercoating layer by vacuum deposition method, asputtering method, or the like to obtain an undercoating layer sample tobe used for measuring the volume resistivity.

For measuring the volume resistivity by an alternating current impedancemethod, a SI 1287 electrochemical interface (manufactured by TOYOCorporation) as a power source, an SI 1260 impedance/gain phase analyzer(manufactured by TOYO Corporation) as an ammeter, and a 1296 dielectricinterface (manufactured by Toyo Corporation) as a current amplifier areused.

Using an aluminum substrate in the AC impedance measurement sample asthe cathode and the gold electrode as the anode, an AC voltage of 1 Vp-pis applied from the high frequency side in a frequency range from 1 MHzto 1 mHz, and the AC impedance of each sample is measured to calculatethe volume resistivity by fitting the Cole-Cole plot graph obtained bythe measurement to an RC parallel equivalent circuit.

The undercoating layer may have a Vickers hardness of 35 or higher.

In order to prevent a moire fringe from occurring, surface roughness(ten-point average roughness) of the undercoating layer may be adjustedfrom 1/(4n) (n is a refractive index of an upper layer) of the exposurelaser wavelength λ to ½ thereof.

In order to adjust the surface roughness, resin particles or the likemay be added to the undercoating layer. Examples of the resin particlesinclude silicone resin particles and crosslinked polymethylmethacrylateresin particles. Further, in order to adjust the surface roughness, thesurface of the undercoating layer may be polished. Examples of apolishing method include buffing, sandblasting treatment, wet honing,and grinding treatment.

Formation of the undercoating layer is not particularly limited and aknown forming method is used. For example, a coating film of anundercoating layer-forming coating liquid obtained by adding the abovecomponents to a solvent is formed, and the coating film is dried to formthe undercoating layer by heating as needed.

Examples of the solvent for preparing the undercoating layer-formingcoating liquid include known organic solvents such as alcohol solvent,aromatic hydrocarbon solvent, halogenated hydrocarbon solvent, ketonesolvent, ketone alcohol solvent, ether solvent, and ester solvent.

Specific examples of these solvents include usual organic solvents suchas methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzylalcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethylketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate,dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene,and toluene.

As a method of dispersing the charge transport material containing atleast one of imide compounds represented by Formula (1) or (2) in theundercoating layer, from the viewpoint of improving film formability ofthe undercoating layer, known methods such as a roll mill, a ball mill,a vibration ball mill, an attritor, a sand mill, a colloid mill, a paintshaker, or the like may be used. Even in a case where the undercoatinglayer further contains inorganic particles, the dispersion may beprepared by the same method.

Examples of a method for applying the undercoating layer-forming coatingliquid onto the conductive substrate include normal methods such as ablade coating method, a wire bar coating method, a spray coating method,a dipping coating method, a bead coating method, an air knife coatingmethod, and a curtain coating method.

[Conductive Substrate]

Examples of the conductive substrate include a metal plate including ametal (such as aluminum, copper, zinc, chromium, nickel, molybdenum,vanadium, indium, gold, and platinum) or an alloy (such as stainlesssteel), a metal drum, and a metal belt. In addition, examples of theconductive substrate also include paper, a resin film, and a belt whichare obtained by applying, vapor-depositing, or laminating a conductivecompound (for example, a conductive polymer, indium oxide, or the like),metal (for example, aluminum, palladium, gold, or the like), or analloy. Here, “conductive” means that the volume resistivity is less than1013 (Ω·cm).

In a case where the electrophotographic photoreceptor is used in a laserprinter, the surface of the conductive substrate preferably roughened tohave a center line average roughness Ra from 0.04 μm to 0.5 μm in orderto prevent interference fringes generated when emitting laser light. Ina case of using non-interference light as a light source, althoughroughening for prevention of interference fringes is not particularlynecessary, since the roughening prevents defects from occurring due toirregularities on the surface of the conductive substrate, it issuitable for longer life.

Examples of a surface-roughening method include wet honing performed bysuspending an abrasive in water and blowing suspension on the conductivesubstrate, centerless grinding performed by pressing the conductivesubstrate against a rotating grindstone and performing continuousgrinding processing, and anodic oxidation.

Examples of the surface-roughening method also include a method in whicha conductive or semi-conductive powder is dispersed in a resin withoutroughening the surface of the conductive substrate to form a layer onthe surface of the conductive substrate and surface-roughening isperformed by particles dispersed in the layer.

The surface roughening treatment by anodic oxidation is to form an oxidefilm on the surface of the conductive substrate by anodizing in anelectrolyte solution using a conductive substrate made of metal (forexample, aluminum) as an anode. Examples of the electrolyte solutioninclude a sulfuric acid solution and an oxalic acid solution. However, aporous anodic oxide film formed by the anodic oxidation is chemicallyactive in the state as it is, is likely to be stained, and has a largechange in resistance depending on the environment. Therefore, the porousanodic oxide film is preferably subjected to a sealing treatment thatfine pores of the oxide film are blocked by volume expansion due tohydration reaction in pressurized water vapor or boiling water (a metalsalt such as nickel may be added) to be changed to a more stablehydrated oxide.

A thickness of the anodic oxide film is preferably, for example, from0.3 μm to 15 μm. When the film thickness is within the above range,there is tendency that barrier properties against injection isexhibited, and there is tendency that residual potential is preventedfrom increasing due to repeated use.

The conductive substrate may also be subjected to a treatment with anacidic treatment solution or a boehmite treatment.

The treatment with the acidic treatment solution is carried out, forexample, as follows. First, an acidic treatment liquid containingphosphoric acid, chromic acid, and hydrofluoric acid is prepared. Amixing ratio of the phosphoric acid, the chromic acid, and thehydrofluoric acid in the acidic treatment solution is, for example, from10% by weight to 11% by weight of phosphoric acid, 3% by weight to and5% by weight of chromic acid, and 0.5% by weight to 2% by weight, and aconcentration of these whole acids may be from 13.5% by weight to 18% byweight. A treatment temperature is preferably, for example, from 42° C.to 48° C. A film thickness of the film to be coated is preferably from0.3 μm to 15 μm.

The boehmite treatment is carried out by, for example, dipping theconductive substrate in deionized water from 90° C. to 100° C. for 5minutes to 60 minutes, or making the conductive substrate in contactwith heated steam from 90° C. to 120° C. for 5 minutes to 60 minutes. Afilm thickness of the film to be coated is preferably from 0.1 μm to 5μm. The anodic oxidation may be further performed using an electrolytesolution having low film solubility such as adipic acid, boric acid,borate, phosphate, phthalate, maleate, benzoate, tartrate, and citrate.

[Photosensitive Layer]

(Charge Generation Layer)

The charge generation layer is, for example, a layer containing a chargegeneration material and a binder resin. Further, the charge generationlayer may be a deposition layer of a charge generation material. Thedeposition layer of the charge generation material is suitable for acase of using an incoherent light source such as a light emitting diode(LED) or an organic electro-luminescence (EL) image array.

Examples of the charge generation material include azo pigments such asbisazo and trisazo; a condensed ring aromatic pigment such asdibromoanthanthrone; a perylene pigment; a pyrrolopyrrole pigment; aphthalocyanine pigment; zinc oxide; and trigonal selenium.

Among these materials, in order to cope with laser exposure in the nearinfrared region, it is preferable to use a metal phthalocyanine pigmentor a metal-free phthalocyanine pigment, as the charge generationmaterial. Specifically, for example, hydroxygallium phthalocyanine;chlorogallium phthalocyanine; dichlorotin phthalocyanine; and titanylphthalocyanine are more preferable.

On the other hand, in order to cope with laser exposure in the nearultraviolet region, as the charge generation material, a condensedaromatic pigment such as dibromoanthanthrone; a thioindigo pigment; aporphyrazine compound; zinc oxide; trigonal selenium; a bisazo pigment;and the like are preferable.

Also in a case of using an incoherent light source having an emissioncenter wavelength from 450 nm to 780 nm, such as an LED or an organic ELimage array, the above charge generation material may be used. However,when a thin film of 20 μm or less is used as the photosensitive layerfrom the viewpoint of resolution, the electric field intensity in thephotosensitive layer increases, and charge reduction due to chargeinjection from the substrate is caused, so that image defect referred toas a so-called black spot tend to occur. The tendency is remarkable whenusing a charge generation material which is likely to cause dark currentin a p-type semiconductor such as trigonal selenium or a phthalocyaninepigment.

On the contrary, when using a n-type semiconductor such as a condensedring aromatic pigment, a perylene pigment, and an azo pigment, as thecharge generation material, it is difficult to generate a dark currentand, even in a thin film, the image defect called a black spot isprevented.

n-Type is determined depending on a polarity of flowing photocurrent byusing a normally used time-of-flight method, and a type in which thephotocurrent is easy to flow using electrons rather than holes ascarriers is determined as the n-type.

The binder resin used for the charge generation layer is selected from awide range of insulating resins. In addition, the binder resin may beselected from organic photoconductive polymers such aspoly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, andpolysilane.

Examples of the binder resin include a polyvinyl butyral resin, apolyarylate resin (such as polycondensate of bisphenols and aromaticdicarboxylic acid), a polycarbonate resin, a polyester resin, a phenoxyresin, a vinyl chloride-vinyl acetate copolymer, a polyamide resin, anacrylic resin, a polyacrylamide resin, a polyvinyl pyridine resin, acellulose resin, a urethane resin, an epoxy resin, casein, a polyvinylalcohol resin, and a polyvinyl pyrrolidone resin. Here, “insulatingproperty” means that the volume resistivity is 10¹³ Ωcm or higher.

One kind of these binder resins is used alone or two or more kindsthereof are used by being mixed.

A mixing ratio of the charge generation material and the binder resin ispreferably from 10:1 to 1:10 in terms of weight ratio.

The charge generation layer may also contain other known additives.

Formation of the charge generation layer is not particularly limited anda known forming method is used. For example, a coating film of a chargegeneration layer-forming coating liquid obtained by adding the abovecomponents to a solvent is formed, and the coating film is dried to formthe charge generation layer by heating as needed. The formation of thecharge generation layer may be carried out by vapor deposition of thecharge generation material. Formation of the charge generation layer bythe vapor deposition is particularly suitable for a case of using acondensed ring aromatic pigment or a perylene pigment as the chargegeneration material.

Examples of a solvent for preparing the charge generation layer-formingcoating liquid include methanol, ethanol, n-propanol, n-butanol, benzylalcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethylketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane,tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, andtoluene. One kind of the solvents is used alone and two or more kindsthereof are used by being mixed.

In a method for dispersing particles (for example, charge generationmaterial) in the charge generation layer-forming coating liquid, forexample, a media dispersing machine such as a ball mill, a vibrationball mill, an attritor, a sand mill, and a horizontal sand mill or amedialess dispersing machine such as a stirrer, an ultrasonic dispersingmachine, a roll mill, and a high-pressure homogenizer is used. Examplesof the high-pressure homogenizer include a collision type in whichdispersing is performed by a liquid-liquid collision or a liquid-wallcollision in a high pressure state, or a penetration type in whichdispersing is performed by penetrating a fine flow path in a highpressure state.

When dispersing is performed, it is effective to set the averageparticle diameter of the charge generation material in the chargegeneration layer-forming coating liquid to 0.5 μm or less, preferably0.3 μm or less, and more preferably 0.15 μm or less.

Examples of a method for coating the undercoating layer (or anintermediate layer) with the charge generation layer-forming coatingliquid include normal methods such as a blade coating method, a wire barcoating method, a spray coating method, a dipping coating method, a beadcoating method, an air knife coating method, and a curtain coatingmethod.

A film thickness of the charge generation layer is set preferably from0.1 μm to 5.0 μm, and more preferably from 0.2 μm to 2.0 μm.

(Charge Transport Layer)

The charge transport layer is, for example, a layer containing a chargetransport material and the binder resin. The charge transport layer maybe a layer containing a polymer charge transport material.

Examples of the charge transport material include electron transportcompounds such as: quinone compounds such as p-benzoquinone, chloranil,bromanil, and anthraquinone; a tetracyanoquinodimethane compound; afluorenone compound such as 2,4,7-trinitrofluorenone; a xanthonecompound; a benzophenone compound; a cyanovinyl compound; and anethylene compound. Examples of the charge transport material alsoinclude hole transporting compounds such as a triarylamine compound, abenzidine compound, an arylalkane compound, an aryl-substituted ethylenecompound, a stilbene compound, an anthracene compound, and a hydrazonecompound. These charge transport materials may be used alone or incombination of two or more thereof, but are not limited thereto.

As the charge transport material, from the viewpoint of charge mobility,a triarylamine derivative represented by the following Formula (a-1) anda benzidine derivative represented by the following Formula (a-2) arepreferable.

In Formula (a-1), Ar^(T1), Ar^(T2), and Ar^(T3) each independentlyrepresent a substituted or unsubstituted aryl group,—C₆H₄—C(R^(T4))═C(R^(T5))(R^(T6)), or —C₆H₄—CH═CH—CH═C(R^(T7))(R^(T8)).R^(T4), R^(T5), R^(T6), R^(T7), and R^(T8) each independently representa hydrogen atom, a substituted or unsubstituted alkyl group, or asubstituted or unsubstituted aryl group.

Examples of the substituent of each of the above groups include ahalogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxygroup having 1 to 5 carbon atoms. Examples of the substituent of each ofthe above groups also include a substituted amino group substituted withan alkyl group having 1 to 3 carbon atoms.

In Formula (a-2), R^(T91) and R^(T92) each independently represent ahydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbonatoms, or an alkoxy group having 1 to 5 carbon atoms. R^(T101), R^(T12),R^(T111), and R^(T112) each independently represent a halogen atom, analkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5carbon atoms, an amino group having 1 or 2 carbon atoms substituted withan alkyl group, a substituted or unsubstituted aryl group,—C(R^(T12))═C(R^(T13))(R^(T14)), or —CH═CH—CH═C(R^(T15))(R^(T16)).R^(T12), R^(T13), R^(T14), R^(T15), and R^(T16) each independentlyrepresent a hydrogen atom, a substituted or unsubstituted alkyl group,or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1, and Tn2each independently represent an integer of 0 to 2.

Examples of the substituent of each of the above groups include ahalogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxygroup having 1 to 5 carbon atoms. Examples of the substituent of each ofthe above groups also include a substituted amino group substituted withan alkyl group having 1 to 3 carbon atoms.

Among the triarylamine derivative represented by Formula (a-1) and thebenzidine derivative represented by Formula (a-2), from the viewpoint ofcharge mobility, a triarylamine derivative having“—C₆H₄—CH═CH—CH═C(R^(T7))(R^(T8))” and a benzidine derivative having“—CH═CH—CH═C(R^(T15))(R^(T16))” are particularly preferable.

As the polymer charge transport material, known materials having chargetransporting ability, such as poly-N-vinylcarbazole and polysilane areused. In particular, a polyester polymer charge transport material isparticularly preferable. The polymer charge transport material may beused alone or may be used in combination with the binder resin.

Examples of the binder resin used for the charge transport layer includea polycarbonate resin, a polyester resin, a polyarylate resin, amethacrylic resin, an acrylic resin, a polyvinyl chloride resin, apolyvinylidene chloride resin, a polystyrene resin, a polyvinyl acetateresin, a styrene-butadiene copolymer, a vinylidenechloride-acrylonitrile copolymer, a vinyl chloride-vinyl acetatecopolymer, a vinyl chloride-vinyl acetate-maleic anhydride copolymer, asilicone resin, silicone alkyd resin, a phenol-formaldehyde resin, astyrene-alkyd resin, poly-N-vinylcarbazole, and polysilane. Among these,the polycarbonate resin or the polyarylate resin is appropriate as thebinder resin. One kind of these binder resins is used alone or two ormore kinds thereof are used.

A mixing ratio of the charge transport material and the binder resin ispreferably from 10:1 to 1:5 in terms of weight ratio.

The charge transport layer may also contain other known additives.

Formation of the charge transport layer is not particularly limited anda known forming method is used. For example, a coating film of a chargetransport layer-forming coating liquid obtained by adding the abovecomponents to a solvent is formed, and the coating film is dried to formcharge transport layer by heating as needed.

Examples of a solvent for preparing the charge transport layer-formingcoating liquid include usual organic solvents such as aromatichydrocarbons such as benzene, toluene, xylene, and chlorobenzene;ketones such as acetone and 2-butanone; halogenated aliphatichydrocarbons such as methylene chloride, chloroform, and ethylenechloride; and cyclic or linear ethers such as tetrahydrofuran and ethylether.

One kind of the solvents is used alone and two or more kinds thereof areused by being mixed.

Examples of an applying method used when applying the charge transportlayer-forming coating liquid onto the charge generation layer includenormal methods such as a blade coating method, a wire bar coatingmethod, a spray coating method, a dipping coating method, a bead coatingmethod, an air knife coating method, and a curtain coating method.

A film thickness of the charge transport layer is set preferably from 5μm to 50 μm, and more preferably from 10 μm to 30 μm.

(Protective Layer)

The protective layer is provided on the photosensitive layer as needed.The protective layer is provided, for example, to prevent thephotosensitive layer from chemically changing at the time of chargingand to further improve the mechanical strength of the photosensitivelayer.

Therefore, a layer configured by a cured film (crosslinked film) may beapplied to the protective layer. Examples of the layer include a layershown in the following 1) or 2).

1) A layer configured by a cured film of a composition containing areactive group-containing charge transport material having a reactivegroup and a charge transporting skeleton in the same molecule (that is,a layer containing a polymer or crosslinked member of the reactivegroup-containing charge transport material)

2) A layer configured by a cured film of a composition containing anon-reactive charge transport material and a reactive group-containingnon-charge transport material having a reactive group without having acharge transporting skeleton (that is, a layer containing a non-reactivecharge transport material and a polymer or a crosslinked member of thereactive group-containing non-charge transport material)

Examples of the reactive group of the reactive group-containing chargetransport material include known reactive groups such as a chainpolymerizable group, an epoxy group, —OH, —OR (where R represents analkyl group), —NH₂, —SH, —COOH, and —SiR^(Q1) _(3-Qn)(OR^(Q2))_(Qn)(where R^(Q1) represents a hydrogen atom, an alkyl group, or asubstituted or unsubstituted aryl group, R^(Q2) represents a hydrogenatom, an alkyl group, or a trialkylsilyl group, and Qn represents aninteger of 1 to 3).

The chain polymerizable group is not particularly limited as long as itis a functional group capable of radical polymerization, and is, forexample, a functional group having a group containing at least a carbondouble bond. Specific examples thereof include a group containing atleast one selected from a vinyl group, a vinyl ether group, a vinylthioether group, a styryl group (vinyl phenyl group), an acryloyl group,a methacryloyl group, and derivatives thereof. Among these, from theviewpoint of excellent reactivity, as the chain polymerizable group, agroup containing at least one selected from the vinyl group, the styrylgroup (vinylphenyl group), the acryloyl group, the methacryloyl group,and derivatives thereof is preferable.

The charge transporting skeleton of the reactive group-containing chargetransport material is not particularly limited as long as it is a knownstructure in an electrophotographic photoreceptor, and examples thereofinclude skeleton derived from a nitrogen-containing hole transportcompound such as a triarylamine compound, a benzidine compound, and ahydrazone compound, in which the skeleton has a structure conjugatedwith a nitrogen atom. Among these, a triarylamine skeleton ispreferable.

The reactive group-containing charge transport material having areactive group and a charge transporting skeleton, the non-reactivecharge transport material, and the reactive group-containing non-chargetransport material may be selected from known materials.

The protective layer may also contain other known additives.

Formation of the protective layer is not particularly limited and aknown forming method is used. For example, a coating film of aprotective layer-forming coating liquid obtained by adding the abovecomponents to a solvent is formed, and the coating film is dried to formthe protective layer by heating as needed.

Examples of the solvent for preparing the protective layer-formingcoating liquid include aromatic solvents such as toluene and xylene;ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, andcyclohexanone; ester solvents such as ethyl acetate and butyl acetate;ether solvents such as tetrahydrofuran and dioxane; cellosolve solventssuch as ethylene glycol monomethyl ether; and alcohol solvents such asisopropyl alcohol and butanol. One kind of the solvents is used aloneand two or more kinds thereof are used by being mixed.

The protective layer-forming coating liquid may be a solventless coatingliquid.

Examples of a method of applying the protective layer-forming coatingliquid onto hotosensitive layer (for example, charge transport layer)include normal methods such as a dipping coating method, an extrusioncoating method, a wire bar coating method, a spray coating method, ablade coating method, a knife coating method, and a curtain coatingmethod.

A film thickness of the protective layer is set, for example, preferablyfrom 1 μm to 20 μm, and more preferably from 2 μm to 10 μm.

[Singlelayer Type Photosensitive Layer]

The singlelayer type photosensitive layer (charge generation/transportlayer) is, for example, a layer containing a charge generation materialand a charge transport material, and further contains a binder resin andother known additives, as needed. These materials are the same as thosedescribed for the charge generation layer and the charge transportlayer.

Then, a content of the charge generation material in the singlelayertype photosensitive layer may be from 10% by weight to 85% by weight,and is preferably from 20% by weight to 50% by weight, based on thetotal solid content. In addition, a content of the charge transportmaterial in the singlelayer type photosensitive layer may be from 5% byweight to 50% by weight, based on the total solid content.

The method of forming the singlelayer type photosensitive layer is thesame as the method of forming the charge generation layer and the chargetransport layer.

A film thickness of the singlelayer type photosensitive layer may befrom 5 μm to 50 μm, and is preferably from 10 μm to 40 μm.

—Image Forming Apparatus and Process Cartridge—

An image forming apparatus according to the exemplary embodimentincludes: an electrophotographic photoreceptor; a charging unit thatcharges a surface of the electrophotographic photoreceptor; anelectrostatic latent image forming unit that forms an electrostaticlatent image on the charged surface of the electrophotographicphotoreceptor; a developing unit that develops the electrostatic latentimage formed on the surface of the electrophotographic photoreceptorwith a developer including toner to form a toner image; and a transferunit that transfers the toner image onto a surface of a recordingmedium. As the electrophotographic photoreceptor, theelectrophotographic photoreceptor according to the exemplary embodimentis adopted.

As the image forming apparatus according to the exemplary embodiment,known image forming apparatuses are adopted. Examples thereof include anapparatus including fixing unit that fixes a transferred toner image toa surface of a recording medium; a direct transfer type apparatus thatdirectly transfers a toner image formed on a surface of anelectrophotographic photoreceptor to a recording medium; an intermediatetransfer type apparatus that primarily transfers a toner image formed ona surface of an electrophotographic photoreceptor to a surface of anintermediate transfer member and secondarily transfers the toner imagetransferred to the surface of the intermediate transfer member onto asurface of a recording medium; an apparatus including a cleaning unitthat cleans a surface of the electrophotographic photoreceptor after thetransfer of the toner image and before charging; an apparatus includingan erasing unit that irradiates a surface of the electrophotographicphotoreceptor after the transfer of a toner image and before charging,with antistatic electricity to erase electricity; and an apparatusincluding an electrophotographic photoreceptor heating unit that raise atemperature of an electrophotographic photoreceptor and reduces arelative temperature.

In a case of the intermediate transfer type apparatus, the transfer unitadopts, for example, a configuration including an intermediate transfermember in which a toner image is transferred on a surface thereof, aprimary transfer unit that primarily transfers the toner image formed onthe surface of the electrophotographic photoreceptor to a surface of theintermediate transfer member, and a secondary transfer unit thatsecondary transfers the toner image transferred to the surface of theintermediate transfer member to a surface of a recording medium.

The image forming apparatus according to the exemplary embodiment may beany of a dry developing type image forming apparatus or a wet developingtype (a developing type using a liquid developer) image formingapparatus.

In the image forming apparatus according to the exemplary embodiment,for example, a portion having an electrophotographic photoreceptor mayhave a cartridge structure (process cartridge) to be attached to anddetached from the image forming apparatus. As the process cartridge, forexample, a process cartridge including the electrophotographicphotoreceptor according to the exemplary embodiment is suitably used. Inthe process cartridge may further include, for example, at least oneselected from the group consisting of a charging unit, an electrostaticlatent image forming unit, a developing unit, and a transfer unit, inaddition to the electrophotographic photoreceptor.

Hereinafter, an example of the image forming apparatus according to theexemplary embodiment will be shown, but the image forming apparatus isnot limited thereto. A main part shown in the figure will be described,and descriptions for the other parts will be omitted.

FIG. 2 is a configuration diagram illustrating an example of the imageforming apparatus according to the exemplary embodiment.

As shown in FIG. 2, the image forming apparatus 100 according to theexemplary embodiment includes a process cartridge 300 having anelectrophotographic photoreceptor 7, an exposure device 9 (an example ofan electrostatic latent image forming unit), a transfer device 40(primary transfer device), and an intermediate transfer member 50. Inthe image forming apparatus 100, the exposure device 9 is disposed at aposition at which the electrophotographic photoreceptor 7 may be exposedfrom an opening of the process cartridge 300, the transfer device 40 isdisposed at a position facing the electrophotographic photoreceptor 7via the intermediate transfer member 50, and the intermediate transfermember 50 is disposed so that a part thereof contacts with theelectrophotographic photoreceptor 7. Although not shown, the imageforming apparatus 100 further includes a secondary transfer device thattransfers the toner image transferred to the intermediate transfermember 50 to a recording medium (for example, paper). The intermediatetransfer member 50, the transfer device 40 (primary transfer device),and the secondary transfer device (not shown) correspond to examples ofthe transfer unit.

The process cartridge 300 in FIG. 2 includes the electrophotographicphotoreceptor 7, a charging device 8 (an example of the charging unit),a developing device 11 (an example of the developing unit), and acleaning device 13 (an example of the cleaning unit), which are in ahousing and are integrally supported. The cleaning device 13 has acleaning blade (an example of a cleaning member) 131. The cleaning blade131 is disposed so as to contact with a surface of theelectrophotographic photoreceptor 7. The cleaning member may be aconductive or insulating fibrous member, instead of an aspect of thecleaning blade 131. The conductive or insulating fibrous member may beused alone or in combination with the cleaning blade 131.

In FIG. 2, as the image forming apparatus, an example of including afibrous member 132 (roll-shaped) that supplies a lubricant 14 to thesurface of the electrophotographic photoreceptor 7 and a fibrous member133 (flat brush shaped) that assists cleaning is shown, but these aredisposed as needed.

Hereinafter, a configuration of the image forming apparatus according tothe exemplary embodiment will be described.

—Charging Device—

As the charging device 8, for example, a contact type charging memberusing a conductive or semiconductive charging roller, a charging brush,a charging film, a charging rubber blade, a charging tube, or the likeis used. In addition, a non-contact type roller charger, a charger knownas it is such as a scorotron charger or a corotron charger using coronadischarge, or the like is also used.

—Exposure Device—

Examples of the exposure device 9 include an optical system device theexposes the surface of the electrophotographic photoreceptor 7 to lightsuch as semiconductor laser light, LED light, liquid crystal shutterlight according to an image data. A wavelength of the light source iswithin a spectral sensitivity range of the electrophotographicphotoreceptor. As a wavelength of the semiconductor laser, near infraredhaving an emission wavelength near 780 nm is mainly used. However, thewavelength is not limited thereto, and an emission wavelength laser of600 nm band or a laser having an emission wavelength from 400 nm to 450nm as blue laser may also be used. In addition, a surface emitting typelaser light source capable of outputting multiple beams is alsoeffective for forming a color image.

—Developing Device—

Examples of the developing device 11 include a general developing devicethat develops an image by contacting or non-contacting with a developer.The developing device 11 is not particularly limited as long as it hasthe above-described function, and is selected according to the purpose.Examples thereof include a known developing machine having a function ofattaching a single-component developer or a two-component developer tothe electrophotographic photoreceptor 7 using a brush, a roller, or thelike. Among the examples, it is preferable to use a developing rollerholding developer on a surface thereof.

The developer used for the developing device 11 may be asingle-component developer of toner alone or a two-component developerincluding toner and a carrier. In addition, the developer may bemagnetic or nonmagnetic. Known developers are adopted to thesedevelopers.

—Cleaning Device—

As the cleaning device 13, a cleaning blade type device including acleaning blade 131 is used.

In addition to the cleaning blade type, a fur brush cleaning type and adevelopment simultaneous cleaning type may be adopted.

—Transfer Device—

Examples of the transfer device 40 include a contact type transfercharger using a belt, a roller, a film, a rubber blade, or the like anda transfer charger known as it is such as a scorotron transfer chargeror a corotron transfer charger using corona discharge.

—Intermediate Transfer Member—

As the intermediate transfer member 50, a belt-shaped member(intermediate transfer belt) containing polyimide, polyamideimide,polycarbonate, polyarylate, polyester, rubber, or the like to whichsemiconductivity is imparted is used. In addition, as a form of theintermediate transfer member, a drum-shaped member may be used inaddition to the belt shape.

FIG. 3 is a configuration diagram illustrating another example of theimage forming apparatus according to the exemplary embodiment.

An image forming apparatus 120 shown in FIG. 3 is a tandem multicolorimage forming apparatus on which four process cartridges 300 aremounted. The image forming apparatus 120 has a configuration in whichfour process cartridges 300 are arranged in parallel on the intermediatetransfer member 50 and one electrophotographic photoreceptor is used foreach color. The image forming apparatus 120 has the same configurationas that of the image forming apparatus 100 except for the tandem type.

Next, the second aspect of the present disclosure will be described indetail.

[Imide Compound]

The imide compound according to the exemplary embodiment has a structurerepresented by the following Formula (1A).

In Formula (1A), Ar represents an aromatic group having 6 to 18 carbonatoms except for a tetravalent perylene group, X¹ and X² eachindependently represent a nitrogen atom or a substituted orunsubstituted carbon atom, Y¹ and Y² each independently represent anoxygen atom, a sulfur atom, a selenium atom, or NH, and R¹ and R² eachindependently represent a hydrogen atom or a monovalent organic group.

An imide compound represented by Formula (1A) (hereinafter also referredto as “specific imide compound”) exhibits a highly electron transportingability. Therefore, the specific imide compound according to theexemplary embodiment is suitable for, for example, an applicationrequired to have electron transporting ability. For example, thespecific imide compound is used for forming a film in photoelectricconversion device (such as an organic EL device and anelectrophotographic photoreceptor), a solar cell, an organic transistor,and the like. Among the applications, the specific imide compound issuitably used for a film or layer required to have an electrontransporting ability in an electrophotographic photoreceptor, and inparticular, is used for a singlelayer type photosensitive layer (aphotosensitive layer having a charge generating ability and a chargetransporting ability) and a photosensitive layer of a laminatedphotoreceptor.

In the related art, an electrophotographic photoreceptor including asinglelayer type photosensitive layer containing a binder resin, acharge generation material, a hole transport material, and an electrontransport material tends to have low compatibility between the binderresin and the electron transport material. When the compatibilitybetween the binder resin and the electron transport material is low, thebinder resin and the electron transport material are separated in thelayer. Accordingly, in an interface at which separation occurs, crackingdefect (also referred to as “crack”) caused by internal stress ormechanical deformation may occur.

In addition, the specific imide compound tends to have highcompatibility with the binder resin. Therefore, it is considered thatcrack is prevented from occurring in the electrophotographicphotoreceptor in which the specific imide compound is contained in thesinglelayer type photosensitive layer.

Next, a structure of a compound according to the exemplary embodimentwill be described in detail.

[Specific Imide Compound]

The specific imide compound according to the exemplary embodiment has astructure represented by Formula (1A).

More specifically, the specific imide compound has an aromatictetracarboxydiimide skeleton. Then, the specific imide compound has astructure in which two nitrogen atoms of the diimide group aresubstituted with a thiazole group, an oxazole group, a selenazole group,an oxadiazole group, or a diazole group each of which may independentlyhave a substituent. (Ar)

In Formula (1A), Ar represents an aromatic group having 6 to 18 carbonatoms.

Examples of an aromatic group having 6 to 18 carbon atoms represented byAr in Formula (1A) include a substituted or unsubstituted aromaticgroup.

Examples of the unsubstituted aromatic group having 6 to 18 carbon atomsinclude a tetravalent aromatic group obtained by removing arbitrary fourhydrogen atoms from an aromatic hydrocarbon such as benzene,naphthalene, anthracene, phenanthrene, tetracene, benzoanthrene(tetraphene), benzophenanthrene (chrysene), triphenylene, pyrene,biphenyl, paraterphenyl, metaterphenyl, and 1-phenylnaphthalene. Here,the aromatic group having 6 to 18 carbon atoms represented by Ar inFormula (1A) does not contain a tetravalent perylene group.

Among the above groups, as the aromatic group represented by Ar inFormula (1A), a tetravalent naphthalene group is preferable.

Positions on the tetravalent aromatic group to be linked to carbon atomsof the imide groups (—N[C═O]₂—) in Formula (1A) are not particularlylimited. The tetravalent aromatic group may be linked to the carbonatoms at arbitrary four points.

Here, the aromatic group having 6 to 18 carbon atoms means that theskeleton including only the aromatic group having no substituent has 6to 18 carbon atoms.

Specific examples of an unsubstituted aromatic group having 6 to 18carbon atoms represented by Ar in Formula (1A) include the followingAr-1 to Ar-8.

Examples of the substituent for the unsubstituted aromatic group having6 to 18 carbon atoms represented by Ar in Formula (1A) include an alkylgroup, an alkoxy group, and a halogen atom (chlorine, iodine, orbromine). Examples of the alkyl group of the alkyl-substituted arylgroup include a linear or branched alkyl group having 1 to 10(preferably 1 to 6 and more preferably 1 to 4) carbon atoms. Examples ofthe alkoxy group of the alkoxy-substituted aryl group include a linearor branched alkoxy group having 1 to 10 (preferably 1 to 6 and morepreferably 1 to 4) carbon atoms.

(X¹ and X²)

In Formula (1A), X¹ and X² each independently represent a nitrogen atomor a substituted or unsubstituted carbon atom.

In a case where X¹ and X² represent a substituted carbon atom in Formula(1A), examples of the substituent which the substituted carbon atom hasinclude an organic group having 1 to 40 carbon atoms.

Among the organic groups having 1 to 40 carbon atoms, the carbon atompreferably has a monovalent organic group formed by combining one ormore kinds of a halogen atom, an aryl group having 6 to 30 carbon atoms,an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an ethergroup, an alkoxy group, and an ester group.

Among the above, the carbon atom more preferably has a monovalent groupformed by combining one or more kinds of an aliphatic hydrocarbon grouphaving 1 to 10 carbon atoms, an ether group, an alkoxy group, and anester group.

Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atomsinclude an alkyl group and an alkylene group.

Examples of the above-described monovalent group include the followinggroups. In the following linking group, “*” represents a bond linked tothe carbon atom represented by X¹ or X² in Formula (1A). R^(A)represents an alkyl group, R^(B) represents an alkylene group, R^(C)represents a halogen atom, and Ar^(A) represents an aryl group. n₁represents an integer of 1 or more. When n₁ represents an integer of 2or more, plural R^(B)'s may be the same or different.

-   -   —OH    -   —R^(A)    -   —O—R^(A)    -   —O—Ar^(A)    -   —R^(B)—O—Ar^(A)    -   —R^(C)    -   —Ar^(A)    -   —R^(B)—C(═O)—R^(A)    -   —R^(B)—OH    -   —Ar^(A)—OH    -   —R^(B)—O—R^(A)    -   —R^(B)—O—Ar^(A)    -   —O—R^(A)    -   —C(═O)—R^(A)    -   —C(═O)—O—R^(A)    -   —C(═O)—OH    -   —R^(B)—C(═O)—O—R^(A)    -   —R^(B)—C(═O)—O—(R^(B)—O)n₁-R^(A)    -   —R^(B)—R^(C)    -   —Ar^(A)-R^(C)    -   —R^(B)—C(═O)—O—R^(B)—Ar^(A)    -   —R^(B)—C(═O)—O—Ar^(A)

Examples of the alkyl group represented by R^(A) include a substitutedor unsubstituted alkyl group.

Examples of the unsubstituted alkyl group represented by R^(A) include alinear alkyl group having 1 to 10 carbon atoms (preferably 1 to 8 carbonatoms) and a branched alkyl group having 3 to 10 carbon atoms(preferably having 5 to 8 carbon atoms).

Examples of the linear alkyl group having 1 to 10 carbon atoms include amethyl group, an ethyl group, a n-propyl group, a n-butyl group, an-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, an-nonyl group, and a n-decyl group.

Examples of the branched alkyl group having 3 to 10 carbon atoms includean isopropyl group, an isobutyl group, a sec-butyl group, a tert-butylgroup, an isopentyl group, a neopentyl group, a tert-pentyl group, anisohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptylgroup, a sec-heptyl group, a tert-heptyl group, an isooctyl group, asec-octyl group, a tert-octyl group, an isononyl group, a sec-nonylgroup, a tert-nonyl group, an isodecyl group, a sec-decyl group, and atert-decyl group.

Among the above groups, as the unsubstituted alkyl group, lower alkylgroups such as the methyl group and the ethyl group are preferable.

Examples of the substituent in the alkyl group represented by R^(A)include an alkoxy group having 1 to 4 carbon atoms, an unsubstitutedaryl group, a phenyl group substituted with an alkyl group or alkoxygroup, having 1 to 4 carbon atoms, an aralkyl group having 7 to 10carbon atoms, a hydroxyl group, a carboxyl group, a nitro group, and ahalogen atom (chlorine, iodine, or bromine).

Examples of the alkoxy group of the alkoxy-substituted alkyl groupinclude a linear or branched alkoxy group having 1 to 10 (preferably 1to 6 and more preferably 1 to 4) carbon atoms. In addition, in a casewhere X¹ and X² in Formula (1A) to be described later are carbon atoms,examples of the aryl group of the aryl-substituted alkyl group includethe same groups as the unsubstituted aryl group which is substituted forthe carbon atom.

As the alkylene group represented by R^(B), groups having a structure inwhich one hydrogen is further removed from the alkyl group representedby R^(A) are preferable.

Examples of the halogen atom represented by R^(C) include a fluorineatom, a chlorine atom, a bromine atom, and an iodine atom.

Examples of the aryl group represented by Ar^(A) include a substitutedor unsubstituted aryl group.

The unsubstituted aryl group is preferably an aryl group having 6 to 30carbon atoms, and examples thereof include a phenyl group, a biphenylgroup, a 1-naphthyl group, a 2-naphthyl group, a 9-anthryl group, a9-phenanthryl group, a 1-pyrenyl group, a 5-naphthacenyl group, a1-indenyl group, a 2-azulenyl group, a 9-fluorenyl group, a terphenylgroup, a quarterphenyl group, o-, m-, and p-tolyl groups, a xylyl group,o-, m-, and p-cumenyl groups, a mesityl group, a pentalenyl group, abinaphthalenyl group, a tanaphthalenyl group, a quaternaphthalenylgroup, a heptarenyl group, a biphenylenyl group, an indacenyl group, afluoranthenyl group, an acenaphthylenyl group, an aceanthrylenyl group,a phenalenyl group, a fluorenyl group, an anthryl group, a bianthracenylgroup, a teranthracenyl group, a quater anthracenyl group, ananthraquinolyl group, a phenanthryl group, a triphenylenyl group, apyrenyl group, a chrysenyl group, a naphthacenyl group, a preadenylgroup, a picenyl group, a perylenyl group, a pentaphenyl group, apentacenyl group, a tetraphenylenyl group, a hexaphenyl group, ahexacenyl group, a rubicenyl group, a coronenyl group, a trinaphthylenylgroup, a heptaphenyl group, a heptacenyl group, a pyranthrenyl group,and an ovalenyl group. Among the above groups, the phenyl group ispreferable.

Examples of the substituent in the aryl group include an alkyl group, analkoxy group, and a halogen atom (chlorine, iodine, or bromine).

Examples of the alkyl group of the alkyl-substituted aryl group includethe same groups as the unsubstituted alkyl group represented by R^(A) inFormula (1A). In addition, in a case where X¹ and X² in Formula (1A) tobe described later are carbon atoms, examples of the alkoxy group of thealkoxy-substituted aryl group include the same groups as theunsubstituted alkoxy group which is substituted for the carbon atom.

In a case where X¹ and X² in Formula (1A) represent a substituted carbonatom, examples of the alkoxy group which the substituted carbon atom mayhave include a substituted or unsubstituted alkoxy group.

In a case where X¹ and X² in Formula (1A) represent a substituted carbonatom, examples of the unsubstituted alkoxy group which the substitutedcarbon atom may have include a linear or branched alkoxy group having 1to 10 (preferably 1 to 6 and more preferably 1 to 4) carbon atoms.

Specific examples of the linear alkoxy group include a methoxy group, anethoxy group, a n-propoxy group, a n-butoxy group, a n-pentyloxy group,a n-hexyloxy group, a n-heptyloxy group, a n-octyloxy group, an-nonyloxy group, and a n-decyloxy group. Specific examples of thebranched alkoxy group include an isopropoxy group, an isobutoxy group, asec-butoxy group, a tert-butoxy group, an isopentyloxy group, aneopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, asec-hexyloxy group, a tert-hexyloxy group, an isoheptyloxy group, asec-heptyloxy group, a tert-heptyloxy group, an isooctyloxy group, asec-octyloxy group, a tert-octyloxy group, an isononyloxy group, asec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, asec-decyloxy group, and a tert-decyloxy group. Among the above groups,as the alkoxy group, the methoxy group is preferable.

In a case where X¹ and X² in Formula (1A) represent a substituted carbonatom, examples of the substituent in the substituted alkoxy group whichthe substituted carbon atom may have include an unsubstituted arylgroup, a phenyl group substituted with an alkyl group, having 1 to 4carbon atoms, an aralkyl group having 7 to 10 carbon atoms, a hydroxylgroup, a carboxyl group, a nitro group, and a halogen atom (chlorine,iodine, or bromine).

Examples of the aryl group of the aryl-substituted alkoxy group includethe same groups as the above-described unsubstituted aryl grouprepresented by Ar^(A).

(Y¹ and Y²)

In Formula (1A), Y¹ and Y² each independently represent an oxygen atom,a sulfur atom, a selenium atom, or NH.

Among the above, atoms represented by Y¹ and Y² in Formula (1A) arepreferably a sulfur atom, an oxygen atom, or a selenium atom, morepreferably a sulfur atom or an oxygen atom, and still more preferably asulfur atom.

(R¹ and R²)

In Formula (1A), R¹ and R² each independently represent a hydrogen atomor a monovalent organic group.

Examples of the monovalent organic group represented by R¹ and R² inFormula (1A) include a monovalent organic group having 1 to 20 carbonatoms.

Among the above groups, the monovalent organic group is preferably agroup formed by combining one or more kinds of a halogen atom, an arylgroup, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, analkoxy group, and an ester group.

In addition, the monovalent organic group is more preferably a groupformed by combining one or more kinds of an aliphatic hydrocarbon grouphaving 1 to 10 carbon atoms, an alkoxy group, and an ester group.

Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atomsinclude an alkyl group and an alkylene group.

Specific examples of the monovalent organic group include the followingorganic groups. In the following linking group, “*” represents a moietylinked to carbon atoms represented by X¹ and X² in Formula (1A). R^(A2)represents an alkyl group, R^(B2) represents an alkylene group, R^(C2)represents a halogen atom, and Ar^(A2) represents an aryl group. n₁represents an integer of 1 or more. When n₁ represents an integer of 2or more, plural R^(B2)'s may be the same or different.

-   -   —R^(A2)    -   —O—R^(A2)    -   —O—Ar^(A2)    -   —R^(B2)—O—Ar^(A2)    -   —R^(C2)    -   —Ar^(A2)    -   —R^(B2)—C(═O)—R^(A2)    -   —R^(B2)—O—R^(A2)    -   —O—R^(A2)    -   —C(═O)—R^(A2)    -   —C(═O)—O—R^(A2)    -   —R^(B2)—C(═O)—O—R^(A2)    -   —R^(B2)—C(═O)—O—(R^(B2)—O)n₁-R^(A2)    -   —R^(B2)—R^(C2)    -   —Ar^(A2)—R^(C2)    -   —R^(B2)—C(═O)—O—R^(B2)-Ar^(A2)    -   —R^(B2)—C(═O)—O—Ar^(A2)

Examples of the alkyl group represented by R^(A2) include a substitutedor unsubstituted alkyl group.

Examples of the unsubstituted alkyl group represented by R^(A2) includean alkyl group having 1 to 10 carbon atoms (preferably 1 to 8 carbonatoms).

In the case where X¹ and X² in Formula (1A) are carbon atoms, examplesof a linear alkyl group having 1 to 10 carbon atoms include the samealkyl groups as the unsubstituted alkyl group which is substituted forthe carbon atom.

As the alkylene group represented by R^(B2), groups having a structurein which one hydrogen is further removed from the alkyl grouprepresented by R^(A2) are preferable.

In the case where X¹ and X² in Formula (1A) are carbon atoms, examplesof the aryl group Ar^(A2) represented by R¹ and R² in Formula (1A)include the same aryl groups as the unsubstituted aryl group Ar^(A1)which is substituted for the carbon atom.

In the case where X¹ and X² in Formula (1A) are carbon atoms, examplesof the alkoxy group represented by R¹ and R² in Formula (1A) include theunsubstituted alkoxy group which is substituted for the carbon atom.

Specific examples of the specific imide compound are shown below, butthe specific imide compound is not limited thereto. An exemplarycompound numbers in the following will be noted as Exemplary Compound(1A-number). Specifically, an exemplary compound 15 will be noted, forexample, as “Exemplary Compound (1A-15)”.

Exem- plary Com- pound Ar —X¹ = ^(*1) —X² = ^(*1) —Y¹— —Y²— —R¹ —R² 1A-1Ar-1 C—H C—H O O H H 1A-2 Ar-1 C—H C—H S S H H 1A-3 Ar-1 C—H C—H S S CH₃CH₃ 1A-4 Ar-1 N N O O Ph Ph 1A-5 Ar-1 C—CH₃ C—CH₃ S S H H 1A-6 Ar-1 C—HC—H S S C(═O)OCH₃ C(═O)OCH₃ 1A-7 Ar-1 C—C(═O)OCH₃ C—C(═O)OCH₃ S S H H1A-8 Ar-1 C—H C—H S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-9 Ar-1C—CH₂C(═O)OCH₂CH₃ C—CH₂C(═O)OCH₂CH₃ S S H H 1A-10 Ar-1 C—CH₂C(═O)OCH₂CH₃C—CH₂C(═O)OCH₂CH₃ S S H H 1A-11 Ar-1 C—CH₃ C—CH₃ S S C(═O)OCH₃ C(═O)OCH₃1A-12 Ar-1 C—CH₃ C—CH₃ S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-13 Ar-1 C—PhC—Ph S S H H 1A-14 Ar-1 C—Ph—Br C—Ph—Br S S H H 1A-15 Ar-2 C—H C—H O O HH 1A-16 Ar-2 C—H C—H S S H H 1A-17 Ar-2 C—H C—H S S CH₃ CH₃ 1A-18 Ar-2 NN O O Ph Ph 1A-19 Ar-2 C—CH₃ C—CH₃ S S H H 1A-20 Ar-2 C—H C—H S SC(═O)OCH₃ C(═O)OCH₃ 1A-21 Ar-2 C—C(═O)OCH₃ C—C(═O)OCH₃ S S H H 1A-22Ar-2 C—H C—H S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-23 Ar-2 C—CH₂C(═O)OCH₂CH₃C—CH₂C(═O)OCH₂CH₃ S S H H 1A-24 Ar-2 C—CH₂C(═O)OCH₂CH₃ C—CH₂C(═O)OCH₂CH₃S S H H 1A-25 Ar-2 C—CH₃ C—CH₃ S S C(═O)OCH₃ C(═O)OCH₃ 1A-26 Ar-2 C—CH₃C—CH₃ S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-27 Ar-2 C—Ph C—Ph S S H H 1A-28Ar-2 C—Ph—Br C—Ph—Br S S H H 1A-29 Ar-2 C—CH₂C(═O)OCH₂CH₃ CH S S H H1A-30 Ar-2 C—CH₂C(═O)O(CH₂)₇—CH₃ C—CH₂C(═O)O(CH₂)₇—CH₃ S S H H 1A-31Ar-2 C—CH₂C(═O)OCH₂CH₂—Ph C—CH₂C(═O)OCH₂CH₂—Ph S S H H 1A-32 Ar-2

S S H H 1A-33 Ar-2

S S H H 1A-34 Ar-2 N N Se Se H H 1A-35 Ar-3 C—H C—H O O H H *1: Withrespect to X¹ being a carbon atom or X² being a carbon atom, the carbonatom at the left end shown in the table means a carbon atom linking to anitrogen atom and a carbon atom in the azole skeleton.

Exem- plary Com- pound Ar —X¹ = ^(*1) —X² = ^(*1) —Y¹— —Y²— —R¹ —R²1A-36 Ar-3 C—H 1A- C—H S S H H 1A-37 Ar-3 C—H C—H S S CH₃ CH₃ 1A-38 Ar-3N N O O Ph Ph 1A-39 Ar-3 C—CH₃ C—CH₃ S S H H 1A-40 Ar-3 C—H C—H S SC(═O)OCH₃ C(═O)OCH₃ 1A-41 Ar-3 C—C(═O)OCH₃ C—C(═O)OCH₃ S S H H 1A-42Ar-3 CH CH S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-43 Ar-3 C—CH₂C(═O)OCH₂CH₃C—CH₂C(═O)OCH₂CH₃ S S H H 1A-44 Ar-3 C—C(═O)OCH₂CH₃ C—C(═O)OCH₂CH₃ S S HH 1A-45 Ar-3 C—CH₂C(═O)OCH₂CH₂—Ph C—CH₂C(═O)OCH₂CH₂—Ph S S H H 1A-46Ar-3

S S H H 1A-47 Ar-4 C—H C—H O O H H 1A-48 Ar-4 C—H C—H S S H H 1A-49 Ar-4C—H C—H S S CH₃ CH₃ 1A-50 Ar-4 N N O O Ph Ph 1A-51 Ar-4 C—CH₃ C—CH₃ S SH H 1A-52 Ar-4 C—H C—H S S C(═O)OCH₃ C(═O)OCH₃ 1A-53 Ar-4 C—C(═O)OCH₃C—C(═O)OCH₃ S S H H 1A-54 Ar-4 C—H C—H S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃1A-55 Ar-4 C—CH₂C(═O)OCH₂CH₃ C—CH₂C(═O)OCH₂CH₃ S S H H 1A-56 Ar-4C—C(═O)OCH₂CH₃ C—C(═O)OCH₂CH₃ S S H H 1A-57 Ar-5 C—C(═O)OCH₃ C—C(═O)OCH₃S S H H 1A-58 Ar-5 C—H C—H S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-59 Ar-5C—CH₂C(═O)OCH₂CH₃ C—CH₂C(═O)OCH₂CH₃ S S H H 1A-60 Ar-5 C—C(═O)OCH₂CH₃C—C(═O)OCH₂CH₃ S S H H 1A-61 Ar-6 C—C(═O)OCH₃ C—C(═O)OCH₃ S S H H 1A-62Ar-6 C—H C—H S S C(═O)OCH₂CH₃ C(═O)OCH₂CH₃ 1A-63 Ar-6 C—CH₂C(═O)OCH₂CH₃C—CH₂C(═O)OCH₂CH₃ S S H H 1A-64 Ar-6 C—C(═O)OCH₂CH₃ C—C(═O)OCH₂CH₃ S S HH 1A-65 Ar-7 C—CH₂C(═O)OCH₂CH₃ C—CH₂C(═O)OCH₂CH₃ S S H H 1A-66 Ar-7C—C(═O)OCH₂CH₃ C—C(═O)OCH₂CH₃ S S H H 1A-67 Ar-8 C—CH₂C(═O)OCH₂CH₃C—CH₂C(═O)OCH₂CH₃ S S H H 1A-68 Ar-8 C—C(═O)OCH₂CH₃ C—C(═O)OCH₂CH₃ S S HH 1A-69 Ar-2 C—H C—H S Se H H 1A-70 Ar-2 C—H C—H S O H H 1A-71 Ar-2 C—HC—H S NH H H 1A-72 Ar-2 C—H C—H Se O H H 1A-73 Ar-2 C—H C—H Se NH H H1A-74 Ar-2 C—H C—H O NH H H 1A-75 Ar-2 C—H C—H NH NH H H 1A-76 Ar-2 C—HC—H S S C(═O)OCH₃ C(═O)OCH₂CH₃ 1A-77 Ar-2 C—H C—H S S CH₃ C(═O)OCH₃ *1:With respect to X¹ being a carbon atom or X² being a carbon atom, thecarbon atom at the left end shown in the table means a carbon atomlinking to a nitrogen atom and a carbon atom in the azole skeleton.[Method of Synthesizing Specific Imide Compound]

Hereinafter, a method of synthesizing the specific imide compound willbe described.

The method of synthesizing the specific imide compound is notparticularly limited, and the specific imide compound may be synthesizedby a known method. For example, as shown below, the specific imidecompound may be synthesized by dehydration condensation of correspondingaromatic tetracarboxylic dianhydride and an aminoazole compound.

In a synthesis reaction of the specific imide compound, a solvent is notnecessarily used. However, when the solvent is used, preferable examplesof the solvent include N,N-dimethylformamide (DMF), dimethylacetamide(DMAc), 1,3-dimethyl-2-imidazolidinone (DMI), N-methyl-2-pyrrolidone(NMP), and dimethyl sulfoxide (DMSO).

Here, for example, in a case of synthesizing a specific imide compoundin which X¹, X², Y¹, Y², R¹, and R² independently have different groupsor atoms, the specific imide compound may be synthesized by dehydrationcondensation of two corresponding aminoazole compounds and an aromatictetracarboxylic dianhydride.

In a case of synthesizing a specific imide compound having an estergroup in R¹ or R², a specific imide compound (1A) having an ester groupis synthesized by reacting the aromatic tetracarboxylic dianhydride withthe aminoazole compound. Thereafter, a specific imide compound (2A)having various ester groups may be synthesized by reacting apredetermined alcohol (R^(ES)—OH) with R¹ or R² by transesterificationreaction in presence of an acid catalyst, as needed.

The acid catalyst in the transesterification reaction is notparticularly limited, and for example, an acid catalyst used in a usualesterification reaction, such as sulfuric acid, toluenesulfonic acid,and trifluoroacetic acid may be used.

The specific imide compound according to the exemplary embodiment may beused for, for example, an electron transport material in anelectrophotographic photoreceptor, a solar cell, and an organictransistor.

[Electrophotographic Photoreceptor]

The electrophotographic photoreceptor according to the exemplaryembodiment includes a conductive substrate, a singlelayer typephotosensitive layer that is disposed on the conductive substrate andincludes an electron transport material containing the specific imidecompound, a binder resin, a charge generation material, and a holetransport material. The electrophotographic photoreceptor may furtherinclude an undercoating layer, a protective layer, and the like, asneeded.

Hereinafter, the electrophotographic photoreceptor according to theexemplary embodiment will be described in detail with reference to thedrawings. In the drawings, the same or corresponding parts are denotedby the same reference numerals, and duplicated description will beomitted.

FIG. 4 is a schematic partial sectional diagram illustrating an exampleof the layer configuration of the electrophotographic photoreceptoraccording to the exemplary embodiment. An electrophotographicphotoreceptor 7C shown in FIG. 4 contains the charge generation materialand the charge transport material in the same layer (a singlelayer typephotosensitive layer 6). The electrophotographic photoreceptor 7C shownin FIG. 4 has a structure in which the undercoating layer 1 is providedon the conductive substrate 4, and the singlelayer type photosensitivelayer 6 is formed thereon. In the electrophotographic photoreceptor 7C,for example, the specific imide compound is contained in the singlelayertype photosensitive layer 6. In the electrophotographic photoreceptorshown in FIG. 4, the undercoating layer 1, the protective layer, and thelike may be provided or also not be provided.

Hereinafter, each layer of the electrophotographic photoreceptoraccording to the exemplary embodiment will be described in detail.Descriptions will be given without reference numerals.

[Conductive Substrate]

Hereinafter, the conductive substrate will be described.

The electrophotographic photoreceptor includes the conductive substrate.

Examples of the conductive substrate include a metal plate including ametal (such as aluminum, copper, zinc, chromium, nickel, molybdenum,vanadium, indium, gold, and platinum) or an alloy (such as stainlesssteel), a metal drum, and a metal belt. In addition, examples of theconductive substrate also include paper, a resin film, and a belt whichare obtained by applying, vapor-depositing, or laminating a conductivecompound (for example, a conductive polymer, indium oxide, or the like),metal (for example, aluminum, palladium, gold, or the like), or analloy. Here, “conductive” means that the volume resistivity is less than1013 (Ω·cm).

In a case where the electrophotographic photoreceptor is used in a laserprinter, the surface of the conductive substrate preferably roughened tohave a center line average roughness Ra from 0.04 μm to 0.5 μm in orderto prevent interference fringes generated when emitting laser light. Ina case of using non-interference light as a light source, althoughroughening for prevention of interference fringes is not particularlynecessary, since the roughening prevents defects from occurring due toirregularities on the surface of the conductive substrate, it issuitable for longer life.

Examples of a surface-roughening method include wet honing performed bysuspending an abrasive in water and blowing suspension on the conductivesubstrate, centerless grinding performed by pressing the conductivesubstrate against a rotating grindstone and performing continuousgrinding processing, and anodic oxidation.

Examples of the surface-roughening method also include a method in whicha conductive or semi-conductive powder is dispersed in a resin withoutroughening the surface of the conductive substrate to form a layer onthe surface of the conductive substrate and surface-roughening isperformed by particles dispersed in the layer.

The surface roughening treatment by anodic oxidation is to form an oxidefilm on the surface of the conductive substrate by anodizing in anelectrolyte solution using a conductive substrate made of metal (forexample, aluminum) as an anode. Examples of the electrolyte solutioninclude a sulfuric acid solution and an oxalic acid solution. However, aporous anodic oxide film formed by the anodic oxidation is chemicallyactive in the state as it is, is likely to be stained, and has a largechange in resistance depending on the environment. Therefore, the porousanodic oxide film is preferably subjected to a sealing treatment thatfine pores of the oxide film are blocked by volume expansion due tohydration reaction in pressurized water vapor or boiling water (a metalsalt such as nickel may be added) to be changed to a more stablehydrated oxide.

A thickness of the anodic oxide film is preferably, for example, from0.3 μm to 15 μm. When the film thickness is within the above range,there is tendency that barrier properties against injection isexhibited, and there is tendency that residual potential is preventedfrom increasing due to repeated use.

The conductive substrate may also be subjected to a treatment with anacidic treatment solution or a boehmite treatment.

The treatment with the acidic treatment solution is carried out, forexample, as follows. First, an acidic treatment liquid containingphosphoric acid, chromic acid, and hydrofluoric acid is prepared. Amixing ratio of the phosphoric acid, the chromic acid, and thehydrofluoric acid in the acidic treatment solution is, for example, from10% by weight to 11% by weight of phosphoric acid, 3% by weight to and5% by weight of chromic acid, and 0.5% by weight to 2% by weight, and aconcentration of these whole acids may be from 13.5% by weight to 18% byweight. A treatment temperature is preferably, for example, from 42° C.to 48° C. A film thickness of the film to be coated is preferably from0.3 μm to 15 μm.

The boehmite treatment is carried out by, for example, dipping theconductive substrate in deionized water from 90° C. to 100° C. for 5minutes to 60 minutes, or contacting the conductive substrate to heatedsteam from 90° C. to 120° C. for 5 minutes to 60 minutes. A filmthickness of the film to be coated is preferably from 0.1 μm to 5 μm.The anodic oxidation may be further performed using an electrolytesolution having low film solubility such as adipic acid, boric acid,borate, phosphate, phthalate, maleate, benzoate, tartrate, and citrate.

[Singlelayer Type Photosensitive Layer]

Hereinafter, the singlelayer type photosensitive layer will bedescribed.

The singlelayer type photosensitive layer contains an electron transportmaterial, a binder resin, a charge generation material, and a holetransport material.

Hereinafter, each material contained in the singlelayer typephotosensitive layer will be described in detail.

(Electron Transport Material)

Hereinafter, the electron transport material will be described.

The photosensitive layer according to the exemplary embodiment containsthe electron transport material containing the specific imide compound.

When the specific imide compound is contained as the electron transportmaterial, the compatibility with the binder resin increases. Therefore,cracks in the photosensitive layer are prevented from occurring.

Other electron transport materials are not particularly limited, butexamples thereof include electron transport compounds such as: quinonecompounds such as p-benzoquinone, chloranil, bromanil, andanthraquinone; a tetracyanoquinodimethane compound; a fluorenonecompound such as 2,4,7-trinitrofluorenone; fluorene compounds such asdicyanomethylene fluorene; a xanthone compound; a benzophenone compound;a cyanovinyl compound; and an ethylene compound.

Specific examples thereof include the following electron transportmaterials ET-1 to ET-9.

A proportion of the specific imide compound in the electron transportmaterial is preferably from 90% by weight to 100% by weight, and morepreferably from 98% by weight to 100% by weight.

A content of the electron transport material in the photosensitive layeris preferably from 5% by weight to 30% by weight and more preferably 10%by weight to 20% by weight, from the viewpoint of preventing cracks inthe photosensitive layer from occurring.

(Binder Resin)

Examples of the binder resin include a polycarbonate resin, a polyesterresin, a polyarylate resin, a methacrylic resin, an acrylic resin, apolyvinyl chloride resin, a polyvinylidene chloride resin, a polystyreneresin, a polyvinyl acetate resin, a styrene-butadiene copolymer, avinylidene chloride-acrylonitrile copolymer, a vinyl chloride-vinylacetate copolymer, a vinyl chloride-vinyl acetate-maleic anhydridecopolymer, a silicone resin, a silicone alkyd resin, aphenol-formaldehyde resin, a styrene-alkyd resin, apoly-N-vinylcarbazole, and a polysilane. One kind of these binder resinsmay be used alone and two or more kinds thereof may be used incombination.

From the viewpoint of preventing point defects of an image to beobtained from occurring, the binder resin is preferably at least oneselected from the group consisting of a polycarbonate resin, a polyesterresin, and a polyarylate resin, and more preferably a polycarbonateresin, and particularly preferably a bisphenol Z polycarbonate resin.

The bisphenol Z polycarbonate resin refers to a polycarbonate resinhaving a bisphenol Z structure, that is, a structure obtained byremoving hydrogen atoms of two hydroxy groups from1,1-bis(4-hydroxyphenyl)cyclohexane.

In addition, from the viewpoint of the film formability of thephotosensitive layer, the binder resin preferably has a viscosityaverage molecular weight from 30,000 to 80,000.

A content R of the binder resin based on the total weight of thephotosensitive layer is preferably within the above-described range.

(Charge Generation Material)

Examples of the charge generation material include azo pigments such asbisazo and trisazo; a condensed ring aromatic pigment such asdibromoanthanthrone; a perylene pigment; a pyrrolopyrrole pigment; aphthalocyanine pigment; zinc oxide; and trigonal selenium.

From the viewpoint of improving sensitivity of the photosensitive layer,the charge generation material is preferably the phthalocyanine pigment.Specifically, examples of the phthalocyanine pigment includehydroxygallium phthalocyanine; chlorogallium phthalocyanine; dichlorotinphthalocyanine; and titanyl phthalocyanine.

From the viewpoint of charge generation efficiency, the chargegeneration material is preferably at least any one of hydroxygalliumphthalocyanine and chlorogallium phthalocyanine, more preferablyhydroxygallium phthalocyanine, and still more preferably V-typehydroxygallium phthalocyanine.

From the viewpoint of charge generation efficiency, the hydroxygalliumphthalocyanine is preferably hydroxygallium phthalocyanine having themaximum peak wavelength from 810 nm to 839 nm in a spectral absorptionspectrum at a wavelength range from 600 nm to 900 nm.

The hydroxygallium phthalocyanine having the maximum peak wavelengthfrom 810 nm to 839 nm has an average particle diameter within a specificrange, and preferably has a BET specific surface area within a specificrange. Specifically, the average particle diameter is preferably 0.20 μmor less, more preferably from 0.01 μm to 0.15 μm. The BET specificsurface area is preferably 45 m²/g or more, more preferably 50 m²/g ormore, and still more preferably from 55 m²/g to 120 m²/g. The averageparticle diameter is a volume average particle diameter, and a valueobtained by measurement using a laser diffraction type particle sizedistribution measuring apparatus (LA-700 manufactured by Horiba. Ltd.).The BET specific surface area is a value obtained by measurement by anitrogen substitution method using a fluid type specific surface areaautomatic measuring apparatus (FLOWSORB II 2300 manufactured by ShimadzuCorporation).

The maximum particle diameter (the maximum value of the primary particlediameter) of the hydroxygallium phthalocyanine is preferably 1.2 μm orless, more preferably 1.0 μm or less, and still more preferably 0.3 μmor less.

The hydroxygallium phthalocyanine preferably has an average particlediameter of 0.2 μm or less, the maximum particle diameter of 1.2 μm orless, and the BET specific surface area of 45 m²/g or more.

The hydroxygallium phthalocyanine is preferably a V-type hydroxygalliumphthalocyanine having diffraction peaks at Bragg angles (2θ±0.2°) of atleast 7.3°, 16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrumusing a Cu Kα characteristic X-ray.

From the viewpoint of improving sensitivity of the photosensitive layer,the chlorogallium phthalocyanine is preferably a compound havingdiffraction peaks at Bragg angles (2θ±0.2°) of 7.4°, 16.6°, 25.5°,28.3°. Preferable ranges of maximum peak wavelength, an average particlediameter, the maximum particle diameter, and a BET specific surface areaof the chlorogallium phthalocyanine is the same as those of thehydroxygallium phthalocyanine.

One kind of the charge generation material may be used alone and two ormore kinds thereof may be used in combination.

A content of the charge generation material in the singlelayer typephotosensitive layer is preferably from 0.1% by weight to 10% by weight,more preferably from 0.5% by weight to 5% by weight, and particularlypreferably from 1% by weight to 3% by weight, based on the total weightof the photosensitive layer.

(Hole Transport Material)

Examples of the hole transport material include hole transportingcompounds such as a triarylamine compound, a benzidine compound, anarylalkane compound, an aryl-substituted ethylene compound, a stilbenecompound, an anthracene compound, and a hydrazone compound.

These hole transport materials may be used alone or in combination oftwo or more thereof, but are not limited thereto.

As the hole transport material, from the viewpoint of charge mobility, atriarylamine derivative represented by the following Formula (B-1) and abenzidine derivative represented by the following Formula (B-2) arepreferable.

(In Formula (B-1), R^(B1) represents a hydrogen atom or a methyl group.n11 represents 1 or 2. Ar^(B1) and Ar^(B2) each independently representa substituted or unsubstituted aryl group,—C₆H₄—C(R^(B3))═C(R^(B4))(R^(B5)), or —C₆H₄—CH═CH—CH═C(R^(B6))(R^(B7)).R^(B3) to R^(B7) each independently represent a hydrogen atom, asubstituted or unsubstituted alkyl group, or a substituted orunsubstituted aryl group.)

Examples of the substituent include a halogen atom, an alkyl grouphaving 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms,and a substituted amino group substituted with an alkyl group having 1to 3 carbon atoms.

(In Formula (B-2), R^(B8) and R^(B8′) may be the same or different fromeach other, and each independently represent a hydrogen atom, a halogenatom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy grouphaving 1 to 5 carbon atoms. R^(B9), R^(B9′), R^(B10), and R^(B10′) maybe the same or different from each other, and each independentlyrepresent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino grouphaving 1 or 2 carbon atoms substituted with an alkyl group, asubstituted or unsubstituted aryl group,—C(R^(B11))═C(R^(B12))(R^(B13)), or —CH═CH—CH═C(R^(B14))(R^(B15)).R^(B11) to R^(B15) each independently represent a hydrogen atom, asubstituted or unsubstituted alkyl group, or a substituted orunsubstituted aryl group. m12, m13, n12, and n13 each independentlyrepresent an integer of 0 to 2.)

Among the triarylamine derivative represented by Formula (B-1) and thebenzidine derivative represented by Formula (B-2), a triarylaminederivative having “—C₆H₄—CH═CH—CH═C(R^(B6))(R^(B7))” and a benzidinederivative having “—CH═CH—CH═C(R^(B14))(R^(B15))” are particularlypreferable.

Specific examples of the hole transport material used in thephotosensitive layer in the exemplary embodiment include the followingcompounds, in addition to the triarylamine derivative represented byFormula (B-1) and the benzidine derivative represented by Formula (B-2).

A content of the hole transport material may be from 10% by weight to50% by weight, and is preferably from 20% by weight to 40% by weight,based on the total solid content of the singlelayer type photosensitivelayer.

(Ratio Between Hole Transport Material and Electron Transport Material)

A ratio between the hole transport material and the electron transportmaterial is preferably from 50:50 to 90:10 and more preferably from60:40 to 80:20 in terms of weight ratio (hole transportmaterial:electron transport material).

In addition, as hole transport material, it is preferable to use atleast one of the triarylamine derivative represented by Formula (B-1)and the benzidine derivative represented by Formula (B-2) and use acompound having a structure represented by the specific imide compoundaccording to the exemplary embodiment, as the electron transportmaterial.

(Other Additives)

The singlelayer type photosensitive layer may contain known otheradditives such as a surfactant, an antioxidant, fine particles (such assilicon carbide), a light stabilizer, and a heat stabilizer. Inaddition, in a case where the singlelayer type photosensitive layer is asurface layer, the singlelayer type photosensitive layer may containfluorine resin particles, silicone oil, or the like.

[Formation of Singlelayer Type Photosensitive Layer]

The singlelayer type photosensitive layer is formed by using aphotosensitive layer-forming coating liquid obtained by adding the abovecomponents to a solvent.

Examples of the solvent include usual organic solvents such as aromatichydrocarbons such as benzene, toluene, xylene, and chlorobenzene;ketones such as acetone and 2-butanone; halogenated aliphatichydrocarbons such as methylene chloride, chloroform, and ethylenechloride; and cyclic or linear ethers such as tetrahydrofuran and ethylether. One kind of the solvents used alone and two or more kinds thereofare used by being mixed.

In a method for dispersing particles (for example, charge generationmaterial) in the photosensitive layer-forming coating liquid, forexample, a media dispersing machine such as a ball mill, a vibrationball mill, an attritor, a sand mill, and a horizontal sand mill or amedialess dispersing machine such as a stirrer, an ultrasonic dispersingmachine, a roll mill, and a high-pressure homogenizer is used. Examplesof the high-pressure homogenizer include a collision type in whichdispersing is performed by a liquid-liquid collision or a liquid-wallcollision in a high pressure state, or a penetration type in whichdispersing is performed by penetrating a fine flow path in a highpressure state.

Examples of a method of applying the photosensitive layer-formingcoating liquid onto the undercoating layer include a dipping coatingmethod, an extrusion coating method, a wire bar coating method, a spraycoating method, a blade coating method, a knife coating method, and acurtain coating method.

A film thickness of the singlelayer type photosensitive layer is setpreferably from 5 μm to 60 μm, and more preferably from 10 μm to 40 μm.

[Undercoating Layer]

Hereinafter, the undercoating layer will be described.

The undercoating layer is, for example, a layer containing inorganicparticles and a binder resin.

Examples of the inorganic particles include inorganic particles having apowder resistance (volume resistivity) from 10² Ω·cm to 10¹¹ Ω·cm.

Among these particles, the inorganic particles having the aboveresistance value may be, for example, metal oxide particles such as tinoxide particles, titanium oxide particles, zinc oxide particles, andzirconium oxide particles, and the zinc oxide particles are particularlypreferable.

A specific surface area of the inorganic particles by a BET method maybe preferably, for example, 10 m²/g or more.

A volume average particle diameter of the inorganic particles may be,for example, from 50 nm to 2,000 nm (preferably from 60 nm to 1,000 nm).

A content of the inorganic particles is, for example, preferably from10% by weight to 80% by weight, and more preferably from 40% by weightto 80% by weight with respect to the binder resin.

The inorganic particles may be subjected to a surface treatment. Two ormore kinds of the inorganic particles, which are subjected to differentsurface treatments or have different particle diameters, may be mixed tobe used.

Examples of a surface treatment agent include a silane coupling agent, atitanate coupling agent, an aluminum coupling agent, and a surfactant.In particular, the silane coupling agent is preferable, and a silanecoupling agent having an amino group is more preferable.

Examples of the silane coupling agent having an amino group include3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, andN,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, but are notlimited thereto.

Two or more kinds of the silane coupling agents may be mixed to be used.For example, the silane coupling agent having an amino group and theother silane coupling agent may be used in combination. Examples of theother silane coupling agent include vinyltrimethoxysilane,3-methacryloxypropyl-tris(2-methoxyethoxy)silane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane,3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and3-chloropropyltrimethoxysilane, but are not limited thereto.

The surface treatment method with the surface treatment agent may be anymethod as long as it is a known method, and either a dry method or a wetmethod may be used.

A throughput of the surface treatment agent is, for example, preferablyfrom 0.5% by weight to 10% by weight, with respect to the inorganicparticles.

Here, the undercoating layer may contain an electron accepting compound(acceptor compound) together with the inorganic particles, from theviewpoint of improving long-term stability of electric characteristicsand carrier blocking property.

Examples of the electron accepting compound include electron transportsubstances such as: quinone compounds such as chloranil and bromoanil; atetracyanoquinodimethane compound; fluorenone compounds such as2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazolecompounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole,2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; a xanthone compound; athiophene compound; and diphenoquinone compounds such as3,3′,5,5′-tetra-t-butyldiphenoquinone.

In particular, as the electron accepting compound, a compound having ananthraquinone structure is preferable. As the compound having ananthraquinone structure include a hydroxyanthraquinone compound, anaminoanthraquinone compound, and an aminohydroxyanthraquinone compoundare preferable, and specifically, for example, anthraquinone, alizarin,quinizarin, antharufine, purpurin, and the like are preferable.

The electron accepting compound may be contained by being dispersed inthe undercoating layer together with the inorganic particles or may becontained in a state of being attached to the surfaces of the inorganicparticles.

Examples of a method of attaching the electron accepting compound to thesurfaces of the inorganic particles include a dry method or a wetmethod.

The dry method is, for example, a method in which while stirringinorganic particles with a mixer or the like having a large shear force,an electron accepting compound is dropped directly or by being dissolvedin an organic solvent, and sprayed together with dry air or nitrogen gasto attach the electron accepting compound to the surfaces of theinorganic particles. When dropping or spraying the electron acceptingcompound, the dropping or spraying the electron accepting compound maybe carried out at a temperature equal to or lower than a boiling pointof the solvent. After dropping or spraying the electron acceptingcompound, baking may further be carried out at 100° C. or higher. Bakingis not particularly limited as long as the baking is carried out at atemperature and time at which electrophotographic characteristics areobtained.

The wet method is, for example, a method in which an electron acceptingcompound is added while dispersing inorganic particles in a solvent bystirring, ultrasonic wave, sand mill, attritor, ball mill, or the like,and is stirred or dispersed, and then the solvent is removed to attachthe electron accepting compound to the surfaces of the inorganicparticles. In the solvent removal method, the solvent is removed, forexample, by filtration or distillation. After removing the solvent,baking may further be carried out at 100° C. or higher. Baking is notparticularly limited as long as the baking is carried out at atemperature and time at which electrophotographic characteristics areobtained. In the wet method, moisture contained in the inorganicparticles may be removed before adding the electron accepting compound.Examples of this method include a method of removing the moisture whilestirring and heating in a solvent, and a method of removing the moistureby azeotropic distillation with a solvent.

The attachment of the electron accepting compound may be carried outbefore or after the inorganic particles are subjected to the surfacetreatment with the surface treatment agent. Also, the attachment of theelectron accepting compound and the surface treatment with the surfacetreatment agent may be carried out at the same time.

A content of the electron accepting compound may be, for example, from0.01% by weight to 20% by weight, and is preferably from 0.01% by weightto 10% by weight in the inorganic particles.

Examples of the binder resin used for the undercoating layer includeknown polymer compounds such as an acetal resin (such as polyvinylbutyral), a polyvinyl alcohol resin, a polyvinyl acetal resin, a caseinresin, a polyamide resin, a cellulose resin, gelatin, a polyurethaneresin, a polyester resin, an unsaturated polyester resin, a methacrylicresin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl acetateresin, a vinyl chloride-vinyl acetate-maleic anhydride resin, a siliconeresin, a silicone-alkyd resin, a urea resin, a phenol resin, aphenol-formaldehyde resin, a melamine resin, a urethane resin, an alkydresin, and an epoxy resin; a zirconium chelate compound; a titaniumchelate compound; an aluminum chelate compound; a titanium alkoxidecompound; an organic titanium compound; and known materials such as asilane coupling agent.

Examples of the binder resin used for the undercoating layer alsoinclude a charge transporting resin having a charge transporting groupand a conductive resin (such as polyaniline).

Among these resins, as the binder resin used for the undercoating layer,resin insoluble in the coating solvent of the upper layer is preferable.In particular, thermosetting resins such as a urea resin, a phenolresin, a phenol-formaldehyde resin, a melamine resin, a urethane resin,an unsaturated polyester resin, an alkyd resin, and an epoxy resin; anda resin obtained by reaction of at least one resin selected from thegroup consisting of a polyamide resin, a polyester resin, a polyetherresin, a methacrylic resin, an acrylic resin, a polyvinyl alcohol resin,and a polyvinyl acetal resin with a curing agent are preferable.

In a case where two or more of these curing resins are used incombination, a mixing ratio thereof is set as needed.

The undercoating layer may also contain electron transport material.

In addition, other electron transport materials may be used incombination. Examples of the electron transport material include:quinone compounds such as p-benzoquinone, chloranil, bromanil, andanthraquinone; a tetracyanoquinodimethane compound; a fluorenonecompound such as 2,4,7-trinitrofluorenone; a xanthone compound; abenzophenone compound; a cyanovinyl compound; and an ethylene compound.

Specifically, Examples of the electron transport material also includethe electron transport materials ET-1 to ET-9 described in the sectionof [Singlelayer Type Photosensitive Layer].

A content of the electron transport material may be, for example, from1% by weight to 50% by weight, is preferably from 5% by weight to 40% byweight, and is more preferably 10% by weight to 30% by weight, based onthe total solid content.

The undercoating layer may also contain various additives in order toimprove environmental stability and improve image quality.

Examples of the additives include known materials such as an electrontransporting pigment of a polycyclic condensed type or an azo type, azirconium chelate compound, a titanium chelate compound, an aluminumchelate compound, a titanium alkoxide compound, an organic titaniumcompound, and a silane coupling agent. The silane coupling agent is usedfor a surface treatment of the inorganic particles as described above,but may be added to the undercoating layer as an additive.

Examples of the silane coupling agent as the additive includevinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane,3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and3-chloropropyltrimethoxysilane.

Examples of the zirconium chelate compound include zirconium butoxide,zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonatezirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconiumacetate, zirconium oxalate, zirconium lactate, zirconium phosphonate,zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconiumstearate, zirconium isostearate, methacrylate zirconium butoxide,stearate zirconium butoxide, and isostearate zirconium butoxide.

Examples of the titanium chelate compound include tetraisopropyltitanate, tetra-n-butyl titanate, butyl titanate dimer,tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitaniumacetylacetonate, titanium octylene glycolate, titanium lactate ammoniumsalt, titanium lactate, titanium lactate ethyl ester, titaniumtriethanolaminate, and polyhydroxy titanium stearate.

Examples of the aluminum chelate compound include aluminum isopropylate,monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris (ethylacetoacetate).

These additives may be used alone or used as a mixture or apolycondensate of plural compounds.

The undercoating layer may have a Vickers hardness of 35 or higher.

In order to prevent a moire fringe from occurring, surface roughness(ten-point average roughness) of the undercoating layer may be adjustedfrom 1/(4n) (n is a refractive index of an upper layer) of the exposurelaser wavelength λ to ½ thereof.

In order to adjust the surface roughness, resin particles or the likemay be added to the undercoating layer. Examples of the resin particlesinclude silicone resin particles and crosslinked polymethylmethacrylateresin particles. Further, in order to adjust the surface roughness, thesurface of the undercoating layer may be polished. Examples of apolishing method include buffing, sandblasting treatment, wet honing,and grinding treatment.

Formation of the undercoating layer is not particularly limited and aknown forming method is used. For example, a coating film of anundercoating layer-forming coating liquid obtained by adding the abovecomponents to a solvent is formed, and the coating film is dried to formthe undercoating layer by heating as needed.

Examples of the solvent for preparing the undercoating layer-formingcoating liquid include known organic solvents such as alcohol solvent,aromatic hydrocarbon solvent, halogenated hydrocarbon solvent, ketonesolvent, ketone alcohol solvent, ether solvent, and ester solvent.

Specific examples of these solvents include usual organic solvents suchas methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzylalcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethylketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate,dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene,and toluene.

Examples of a method for dispersing inorganic particles when preparingthe undercoating layer-forming coating liquid include known methods suchas a roll mill, a ball mill, a vibration ball mill, an attritor, a sandmill, a colloid mill, and a paint shaker.

Examples of a method for applying the undercoating layer-forming coatingliquid onto the conductive substrate include normal methods such as ablade coating method, a wire bar coating method, a spray coating method,a dipping coating method, a bead coating method, an air knife coatingmethod, and a curtain coating method.

A film thickness of the undercoatinglayer is set, for example,preferably 3 μm or more, and more preferably from 10 μm to 50 μm.

—Image Forming Apparatus and Process Cartridge—

With respect to the image forming apparatus and the process cartridgeaccording to the second aspect, all the description regarding the imageforming apparatus and the process cartridge according to the firstaspect may be adopted.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples, but the present invention is not limited to thefollowing Examples. Unless otherwise specified, “part” means “part byweight”.

—Preparation of Electrophotographic Photoreceptor—

Example 1

(Preparation of Undercoating Layer)

34 parts by weight of Imide Compound (1-9) represented by Formula (1)are mixed with a solution prepared by dissolving 20 parts by weight of acuring resin raw material (blocked isocyanate, SUMIDUR BL 3175,manufactured by Sumitomo Bayer Urethane Co., Ltd., solid content 75%)and 7.5 parts by weight of butyral resin (S-LEC BL-1, manufactured bySekisui Chemical Co., Ltd.) in 143 parts by weight of methyl ethylketone and dispersed for 120 minutes with a sand mill using 1 mmφ glassbeads to obtain a dispersion.

0.005 parts by weight of dioctyltin dilaurate as a catalyst and 10 partsby weight of silicone resin particles (TOSPEARL145, manufactured by GEToshiba Silicones) are added to the obtained dispersion to obtain anundercoating layer-forming coating liquid. The coating liquid isdipping-applied onto an aluminum substrate by a dipping coating method,and dried and cured at 160° C. for 60 minutes to obtain an undercoatinglayer 1 having a thickness of 4 μm.

(Preparation of Charge Generation Layer)

A mixture including 15 parts by weight of hydroxygallium phthalocyaninehaving diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°,16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrum using a Cu Kαcharacteristic X-ray as the charge generation substance, 10 parts byweight of vinyl chloride-vinyl acetate copolymer resin (VMCH,manufactured by Nippon Unicar Company Limited) as a binder resin, and200 parts by weight of n-butyl acetate are dispersed by stirring for 4hours with a sand mill using glass beads having a diameter of 1 mmφ. 175parts by weight of n-butyl acetate and 180 parts by weight of methylethyl ketone are added to the obtained dispersion and stirred to obtaina charge generation layer-forming coating liquid. This charge generationlayer-forming coating liquid is dipping-applied onto the undercoatinglayer. Thereafter, drying is performed at 140° C. for 10 minutes to forma charge generation layer having a film thickness of 0.2 μm.

(Preparation of Charge Transport Layer)

40 parts by weight of charge transporting agent (HT-1), 8 parts byweight of charge transporting agent (HT-2), and 52 parts by weight ofpolycarbonate resin (A) (viscosity average molecular weight: 50,000) areadded to 800 parts by weight of tetrahydrofuran, and dissolved therein.8 parts by weight of tetrafluoroethylene resin (manufactured by DaikinIndustries Ltd., LUBRON L5, average particle diameter of 300 nm) isadded thereto and dispersed at 5500 rpm for 2 hours using a homogenizer(ULTRA-TURRAX manufactured by IKA) to obtain a charge transportlayer-forming coating liquid. This coating liquid is applied onto theabove-described charge generation layer. Thereafter, drying is performedat 140° C. for 40 minutes to form a charge transport layer having a filmthickness of 27 μm. In this manner, an electrophotographic photoreceptor1 is obtained.

Examples 2 to 9

Except that a kind of the imide compound is changed from the imidecompound (1-9) represented by Formula (1) to the formulation shown inTable 1 in an undercoating layer forming step of Example 1, the sameoperation as in Example 1 are performed to obtain eachelectrophotographic photoreceptor.

Example 10

The same operation as in Example 1 is performed except that theundercoating layer forming step of Example 1 is changed to the followingstep with a kind and amount of the curing resin being changed to 30parts by weight of a phenol resin, to thereby obtain aelectrophotographic photoreceptor.

90 parts by weight of methyl ethyl ketone and 50 parts by weight ofisopropanol are added to 30 parts by weight of resol type phenol resin(PL-4852, manufactured by Gunei Chemical Industry Co., Ltd., nonvolatilecomponent 75%). 34 parts by weight of the imide compound (1-9)represented by Formula (1) is mixed thereto and dispersed with a sandmill for 90 minutes using 1 mmφ glass beads to obtain the undercoatinglayer-forming coating liquid. The coating liquid is dipping-applied ontoan aluminum substrate by a dipping coating method, and dried and curedat 160° C. for 60 minutes to obtain an undercoating layer having athickness of 4 μm.

Example 11

The same operation as in Example 1 is performed except that theundercoating layer forming step of Example 1 is changed to the followingstep while the undercoating layer containing the charge transportmaterial and the curing resin further includes metal oxide particles tothereby obtain an electrophotographic photoreceptor.

100 parts by weight of zinc oxide (manufactured by Tayca Corporation,average particle diameter: 70 nm, specific surface area value: 15 m²/g)is mixed to 600 parts by weight of toluene by stirring, and 1.2 parts byweight of a silane coupling agent (KBM 602, manufactured by Shin-EtsuChemical Co., Ltd.) is added thereto and stirred for 2 hours.Thereafter, toluene is distilled off by distillation under reducedpressure and baked at 125° C. for 2 hours to obtain zinc oxidesurface-treated with a silane coupling agent.

50 parts by weight of the zinc oxide after surface treated, 15 parts byweight of curing agent (blocked isocyanate, SUMIDUR BL 3175,manufactured by Sumitomo Bayer Urethane Co., Ltd.), and 15 parts byweight of butyral resin (S-LEC BL-1, manufactured by Sekisui ChemicalCo., Ltd.) are dissolved in 90 parts by weight of methyl ethyl ketone.35 parts by weight of obtained solution is mixed with 50 parts by weightof methyl ethyl ketone and 10 parts by weight of the electrontransporting compound (1-9) and dispersed with a sand mill for 60minutes using 1 mmφ glass beads to obtain a dispersion.

0.005 parts by weight of dioctyltin dilaurate as a catalyst and 30 partsby weight of silicone resin particles (TOSPEARL145, manufactured by GEToshiba Silicones) are added to the obtained dispersion to obtain anundercoating layer-forming coating liquid. The coating liquid is appliedonto an aluminum substrate by a dipping coating method, and dried andcured at 160° C. for 60 minutes to obtain an undercoating layer having athickness of 10 μm.

Example 12

In an undercoating layer forming step of Example 11, except that 50parts by weight of zinc oxide after surface treated is changed 8 partsby weight of zinc oxide after surface treated, the same operation as inExample 11 are performed to obtain an electrophotographic photoreceptor.

Example 13

Except that 20 parts by weight of a curing resin raw material (blockedisocyanate, SUMIDUR BL 3175, manufactured by Sumitomo Bayer UrethaneCo., Ltd., solid content 75%) and 7.5 parts by weight of butyral resin(S-LEC BL-1, manufactured by Sekisui Chemical Co., Ltd.) are changed to27.5 parts by weight of a modified nylon resin (LUCKAMIDE 5003,manufactured by DIC Corporation) and the solvent is changed to methanolin the undercoating layer forming step of Example 1, the same operationas in Example 1 are performed to obtain the electrophotographicphotoreceptor.

Comparative Examples 1 to 3

The same operation as in Example 1 is performed except that, withrespect to a kind of the imide compound in an undercoating layer formingstep of Example 1, the imide compound (1-9) represented by Formula (1)is changed to the following compound (A), compound (B), or compound (C),to thereby obtain each electrophotographic photoreceptor.

Comparative Example 4

The same operation as in Example 1 is performed except that the imidecompound is not used in the undercoating layer forming step of Example1, to thereby obtain an electrophotographic photoreceptor.

[Evaluation]

The following evaluation is performed for the electrophotographicphotoreceptors prepared as above. Evaluation results are shown in Table1.

—Black Spot Image Quality Evaluation—

For an image quality evaluation, the electrophotographic photoreceptoris mounted on a copying machine “DocuCentre C5570” (manufactured by FujiXerox Co., Ltd.) and 20,000 sheets of 20% halftone images are printedunder an environment of a room temperature of 30° C. and a humidity of85%. After 10 hours, printing is conducted again, and the presence orabsence of black spots is evaluated with respect to an image on the 10thsheet with reference to the following criteria.

A: No black spot.

B: 10 spots or less, which is acceptable for image quality.

C: 10 spots or more occur, which becomes a problem in practical use.

—Residual Potential Evaluation—

In the above-described conditions for evaluating black spot imagequality, a difference ΔV between an initial surface potential and asurface potential after printing 20,000 sheets is calculated forevaluation.

A: 50 V or less, which is no problem.

B: more than 50 V and less than 80 V, which is acceptable.

C: 80 V or more, which becomes a problem in image quality.

TABLE 1 Evaluation Black spot Residual Imide compound Curing resin imagepotential Parts by Parts by quality evalu- Kinds weight Kinds weightevaluation ation Example 1 1-9 34 Polyure- 20 A A thane Example 2 1-6 34Polyure- 20 A A thane Example 3 1-8 34 Polyure- 20 A A thane Example 4 1-15 34 Polyure- 20 A A thane Example 5  1-16 34 Polyure- 20 A A thaneExample 6  1-23 34 Polyure- 20 A A thane Example 7 2-7 34 Polyure- 20 AA thane Example 8 2-8 34 Polyure- 20 A A thane Example 9 2-9 34 Polyure-20 A A thane Example 10 1-9 34 Phenol 30 A A resin Example 11 1-9 10Polyure- 15 A A thane Example 12 1-9 10 Polyure- 15 B B thane Example 131-9 34 Modifi- 27.5 B B ed nylon resin Comparative Com- 34 Polyure- 20 CC Example 1 pound thane (A) Comparative Com- 34 Polyure- 20 C C Example2 pound thane (B) Comparative Com- 34 Polyure- 20 C B Example 3 poundthane (C) Comparative — — Polyure- 20 C C Example 4 thane

From the results shown in Table 1, it is found that theelectrophotographic photoreceptors according to the exemplary embodimentprevent an increase of the residual potential which may be caused whenimages are formed repeatedly, as compared with the electrophotographicphotoreceptor of the comparative examples. In addition, it is found thatthe electrophotographic photoreceptors according to the exemplaryembodiment also prevent black spot image quality from occurring, ascompared with the electrophotographic photoreceptor of the comparativeexamples.

—Synthesis Example of Specific Imide Compound—

(Synthesis Example: Exemplary Compound 1A-23)

26.82 g (0.1 mol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride isdissolved in 150 ml of N,N-dimethylformamide, and 39.11 g (0.21 mol) ofethyl 2-amino-4-thiazolylacetate is added thereto, and the mixture isstirred at 150° C. for 3 hours. A reaction solution is cooled to a roomtemperature, and the precipitated crystals are filtered, and washed with500 ml of methanol to obtain 48 g of gray white crystals. The obtainedcrystals are dissolved in 1 L of chloroform and purified by silica gelchromatography to obtain 39 g of light yellow crystals of the specificimide compound (Exemplary Compound 1A-23) as a targeted substance. Amelting temperature is 257° C. to 259° C. FIG. 5 shows ¹H-NMR spectrumof the obtained specific imide compound (Exemplified Compound 1A-23) indeuterated chloroform solvent at room temperature (25° C.).

Synthesis Example: Exemplary Compound 1A-30

6 g (0.01 mol) of Exemplary Compound 1A-23 obtained as above issuspended in 70 ml of n-octanol, and 0.1 g of sulfuric acid is addedthereto. The mixture is heated and stirred at 140° C. for 5 hours in aflask equipped with a Dean-Stark apparatus. The reaction solution iscooled to a room temperature, and the precipitated crystals arefiltered, and washed with methanol. The obtained crystals are dried witha vacuum drier to obtain 4.6 g of the specific imide compound (ExemplaryCompound 1A-30). A melting temperature is 210° C. to 212° C. FIG. 6shows ¹H-NMR spectrum of the obtained specific imide compound(Exemplified Compound 1A-30) in deuterated chloroform solvent at roomtemperature (25° C.).

Synthesis Example: Exemplary Compound 1A-31

Except that 60 ml of phenethyl alcohol is used in place of 70 ml ofn-octanol in the synthesis of Exemplary Compound 1A-30, reaction isperformed in the same manner to obtain 3.9 g of the specific imidecompound (Exemplary Compound 1A-31). A melting temperature is 215° C. to219° C. FIG. 7 shows ¹H-NMR spectrum of the obtained specific imidecompound (Exemplified Compound 1A-31) in deuterated chloroform solventat room temperature (25° C.).

Synthesis Example: Exemplary Compound 1A-33

30 ml of 1-ethoxy-2-propanol is used in place of 70 ml of n-octanol inthe synthesis of Exemplary Compound 1A-30, and 60 ml of toluene isfurther added thereto. The mixture is heated and refluxed for 4 hours.The reaction solution is cooled to a room temperature. 500 ml ofmethanol is added to the reaction solution to precipitate crystals,followed by filtration. The obtained crystals are purified by silica gelchromatography using a mixed solvent (toluene/tetrahydrofuran=3/1) toobtain 2.7 g of the specific imide compound (Exemplary Compound 1A-33).A melting temperature is 184° C. to 187° C. FIG. 8 shows ¹H-NMR spectrumof the obtained specific imide compound (Exemplified Compound 1A-33) indeuterated chloroform solvent at room temperature (25° C.).

Example 1A

(Preparation of Photoreceptor)

2 parts by weight of hydroxygallium phthalocyanine having diffractionpeaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and28.0° in an X-ray diffraction spectrum using a Cu Kα characteristicX-ray as the charge generation substance, 5 parts by weight of thespecific imide compound (Exemplary Compound 1A-23) as the electrontransport material, 49 parts by weight of copolymer type polycarbonateresin (B) (viscosity average molecular weight of 50,000) as the binderresin, 200 parts by weight of tetrahydrofuran, and 100 parts by weightof monochlorobenzene are mixed. This mixture is dispersed for 6 hours bya sand mill using glass beads having a diameter of 1 mmφ. 31 parts byweight of a hole transport compound (HT-7) and 0.001 parts by weight ofsilicone oil KP 340 (manufactured by Shin-Etsu Chemical Co., Ltd) areadded to the obtained dispersion, and stirred overnight to obtain aphotosensitive layer-forming coating liquid.

The photosensitive layer-forming coating liquid obtained as describedabove is applied onto an aluminum substrate having a diameter of 30 mmby a dipping coating method and dried at 140° C. for 1 hour to form asinglelayer type photosensitive receptor having a film thickness of 26μm.

Example 2A to 6A

Except that a kind of the electron transport material is changed fromExemplary Compound 1A-23 to other specific imide compound shown in Table2, a singlelayer type photosensitive receptor is obtained in the samemanner as Example 1A.

Examples 7A to 10A

Except that kinds of the electron transport material, the chargegeneration material, and the hole transport material are changed toother materials shown in Table 2, a singlelayer type photosensitivereceptor is obtained in the same manner as Example 1A.

Comparative Examples 1A to 4A

Except that kinds of the electron transport material, the hole transportmaterial, and charge generation material are changed to other materialsshown in Table 2, a singlelayer type photosensitive receptor is obtainedin the same manner as Example 1A.

Except that compounds corresponding to Comparative Compounds 1A to 4Aare used as raw materials in the synthesis example of Exemplary Compound1A-23 which is the specific imide compound, Comparative Compounds 1A to4A are synthesized in the same manner.

—Evaluation—

The electrophotographic photoreceptors of Examples 1A to 10A andComparative Examples 1A to 4A prepared above are mounted on DocuCentre-VC7775 (manufactured by Fuji Xerox Co., Ltd.), and the followingevaluations are carried out. Evaluation results are shown in Table 2.

[Blurry Image Quality Evaluation (Density Unevenness)]

An image quality evaluation is performed after 6,000 sheets of 100%black solid images are output using HL-2360D (manufactured by BrotherIndustries, Ltd.) under an environment of a room temperature of 28° C.and a humidity of 85%. The presence or absence of blurring of the imageon the 6,000-th sheet is evaluated with reference to the followingcriteria.

A: blurring of images does not occur.

B: Although some slight faintness may be confirmed on a paper shortside, there is no problem in image quality.

C: White spots occur obviously, which becomes a problem in practicaluse.

[Charge Retention Characteristic Evaluation]

For the electric characteristics of the electrophotographicphotoreceptor, a surface potential probe is provided in a region to bemeasured at a position 1 mm away from the surface of theelectrophotographic photoreceptor using an electrostatic voltmeter (TREK334, manufactured by Trek Japan), the surface potential after chargingis set to −720 V, and the surface potential after outputting 15,000sheets is measured. Thereafter, an evaluation is performed withreference to the following criteria. Drop in charging potential isevaluated.

A: Potential drop is 15 V or less, which is no problem.

B: Potential drop is more than 15 V and less than 25 V, which is noproblem since it is an adjustable range.

C: Potential drop is 25 V or more, which is not adjustable.

[Crack Resistance Evaluation]

0.4 ml of 1 wt % hexane solution of oleic acid is sprayed onto theelectrophotographic photoreceptor and allowed to stand at a roomtemperature (25° C.) for 2 weeks. Thereafter, fractures (cracks) on thesurface of the electrophotographic photoreceptor are evaluated withreference to the following criteria. The microscope used is a digitalmicroscope (model number: VHX-700, manufactured by Keyence Corporation).Observation is performed by magnifying 700 times.

A: When observing with a microscope, there is no problem.

B: When observing with a microscope, fine cracks are observed, but whichis no problem in practical use.

C: It is possible to visually confirm cracks.

TABLE 2 Charge generation Hole transport Blurr Charge retention Crackmaterial material Electron transport material evaluation characteristicresistance Example 1A hydroxygallium HT-7 Exemplary Compound 1A-23 A A Aphthalocyanine Example 2A hydroxygallium HT-7 Exemplary Compound 1A-30 AA A phthalocyanine Example 3A hydroxygallium HT-7 Exemplary Compound1A-31 A A A phthalocyanine Example 4A hydroxygallium HT-7 ExemplaryCompound 1A-33 A A A phthalocyanine Example 5A hydroxygallium HT-7Exemplary Compound 1A-45 A A A phthalocyanine Example 6A hydroxygalliumHT-7 Exemplary Compound 1A-55 A A A phthalocyanine Example 7Achlorogallium HT-1 Exemplary Compound 1A-31 A A A phthalocyanine Example8A chlorogallium  HT-13 Exemplary Compound 1A-33 A A A phthalocyanineExample 9A X-type metal-free HT-7 Exemplary Compound 1A-31 A A Aphthalocyanine Example 10A X-type metal-free HT-7 Exemplary Compound1A-33 A A A phthalocyanine Comparative hydroxygallium HT-7 ComparativeCompound 1A C B C Example 1 A phthalocyanine Comparative hydroxygalliumHT-7 Comparative Compound 2A B C B Example 2A phthalocyanine Comparativehydroxygallium HT-7 Comparative Compound 3A C C C Example 3Aphthalocyanine Comparative chlorogallium HT-7 Comparative Compound 4A BC B Example 4A phthalocyanine

From the results, it is found that the electrophotographic photoreceptoraccording to Examples 1A to 10A has improved crack resistance, ascompared with the electrophotographic photoreceptor of ComparativeExamples 1A to 4A.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An electrophotographic photoreceptor comprising:a conductive substrate; a photosensitive layer provided on theconductive substrate; and an undercoating layer that is provided betweenthe conductive substrate and the photosensitive layer and includes acharge transport material containing at least one of imide compoundsrepresented by Formula (1) or (2):

(in Formulas (1) and (2), R¹⁰, R¹¹, R²⁰, or R²¹ independently representsa group represented by Formula (3) or (4); and in Formulas (3) and (4),X represents a monovalent organic group having at least one of an alkylgroup, an alkylene group, an ether group, an ester group, and a ketogroup, a halogen atom, a nitro group, an aralkyl group, or an arylgroup, Y represents a sulfur atom or an oxygen atom, n represents aninteger of 0 to 2, and when n represents 2, two X's may be the same ordifferent).
 2. The electrophotographic photoreceptor according to claim1, wherein X in Formula (3) or (4) in the imide compound represents amonovalent organic group having at least one of an alkyl group, analkylene group, an ether group, an ester group, and a keto group.
 3. Theelectrophotographic photoreceptor according to claim 1, wherein acontent of the imide compound represented by Formula (1) or (2) in theundercoating layer is from 10% by weight to 80% by weight.
 4. Theelectrophotographic photoreceptor according to claim 1, wherein theundercoating layer contains at least one kind of metal oxide particlesselected from the group consisting of zinc oxide, titanium oxide, andtin oxide.
 5. The electrophotographic photoreceptor according to claim4, wherein a content of the metal oxide particles in the undercoatinglayer is from 10% by weight to 80% by weight.
 6. The electrophotographicphotoreceptor according to claim 1, wherein the undercoating layerfurther contains a curing resin, and the curing resin is at least oneselected from the group consisting of a phenol resin, a melamine resin,a guanamine resin, and a urethane resin.
 7. The electrophotographicphotoreceptor according to claim 6, wherein the curing resin contains aurethane resin.
 8. A process cartridge that is detachable from an imageforming apparatus, the process cartridge comprising: theelectrophotographic photoreceptor according to claim
 1. 9. An imageforming apparatus comprising: the electrophotographic photoreceptoraccording to claim 1; a charging unit that charges a surface of theelectrophotographic photoreceptor; an electrostatic latent image formingunit that forms an electrostatic latent image on a charged surface ofthe electrophotographic photoreceptor; a developing unit that developsthe electrostatic latent image formed on the surface of theelectrophotographic photoreceptor with a developer including toner toform a toner image; and a transfer unit that transfers the toner imageonto a surface of a recording medium.